Embedding models are crucial to modern NLP. However, the creation of the most effective models relies on carefully constructed supervised finetuning data. For high resource languages, such as English, such datasets are readily available. However, for hundreds of other languages, they are simply non-existent. We investigate whether the advent of large language models can help to bridge this gap. We test three different strategies for generating synthetic triplet data used to optimise embedding models. These include in-context learning as well as two novel approaches, leveraging adapter composition and cross lingual finetuning of the LLM generator (XL-LoRA) respectively. We find that while in-context learning still falls short of strong non-synthetic baselines, adapter composition and XL-LoRA yield strong performance gains across a wide array of tasks and languages, offering a clear, scalable pathway to producing performant embedding models for a wide variety of languages.
Figures & tables
Figure 1: Pipeline overview: data is synthesised using an LLM, the result of which is then used to finetune an encoder, resulting in the final embedding model.
Figure 2: XL-LoRA training data construction. Starting with high quality translations we generate positives and negatives based on English, before swapping back the anchor to the original non-English language. Resulting examples are used to finetune the XL-LoRA generator.
XLM-R
MM-BERT
Method
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Score
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Score
Base Encoder
56.2
52.7
55.7
46.3
46.7
4.1
60.8
46.1
72.0
63.8
70.7
66.8
52.2
21.7
62.0
58.5
Unsupervised
74.8 ± 0.3
69.7 ± 0.2
77.1 ± 0.2
76.2 ± 0.3
39.2 ± 0.3
45.4 ± 0.7
70.9 ± 0.3
64.7 ± 0.2
75.5 ± 1.2
58.0 ± 2.6
68.6 ± 1.3
62.1 ± 3.5
44.7 ± 1.7
25.5 ± 1.2
58.0 ± 2.9
56.1 ± 0.8
Cross Lingual
78.0 ± 0.3
77.4 ± 0.1
81.6 ± 0.2
80.9 ± 0.7
47.1 ± 0.6
48.2 ± 1.0
79.9 ± 0.1
70.4 ± 0.2
78.0 ± 0.4
77.7 ± 0.1
79.8 ± 0.4
73.6 ± 0.6
49.3 ± 0.6
29.4 ± 1.7
79.6 ± 0.1
66.8 ± 0.4
Synth - Prompting
81.4 ± 0.5
77.9 ± 0.3
82.3 ± 0.3
81.4 ± 0.5
38.3 ± 0.9
47.4 ± 1.2
69.9 ± 0.5
68.4 ± 0.2
80.6 ± 0.3
76.8 ± 0.4
76.3 ± 0.6
76.6 ± 0.3
41.3 ± 1.0
45.2 ± 1.4
68.0 ± 0.4
66.4 ± 0.4
Synth - Adapter Composition
80.4 ± 0.3
77.6 ± 0.2
84.8 ± 0.2
83.0 ± 0.2
46.4 ± 0.3
49.5 ± 0.5
74.7 ± 0.6
70.9 ± 0.2
79.9 ± 0.3
77.6 ± 0.2
82.2 ± 0.4
81.1 ± 0.4
46.2 ± 0.6
42.1 ± 1.4
72.6 ± 0.9
68.8 ± 0.2
Table 1: Embedding performance on STS tasks (Spearman’s correlation). We report results for two backbones, with mean ± standard deviation over four random seeds where applicable.
Figure 3: Retrieval results across multiple benchmarks. Results are averaged across backbones (XLM-R and mmBERT) and across languages. Metric is recall@10. Full results for all tasks and backbones can be found in Appendix A.7 , but reflect the same clear trend depicted here.
Data type
Anchor
Positive
Hard Negative
Example 1
Annotated
yeah it’s really sad i don’t know i just think um
That’s a sad thing.
Its an uplifting topic to talk about.
Synthetic - Prompted
The person appears to be expressing emotional distress and uncertainty.
yeah it’s great I’m sure I just feel like yeah
Synthetic - LoRA
Yes, I agree that is really sad.
Yeah I know, it’s actually very happy.
Example 2
Annotated
that one person has total control and i always figured at least in a day care center there are other people around and if you get one bad apple there’s are at least other people that can see it they can watch and i just kind of always felt that the chances of something happening were less
It seems like even though there are some bad kids in daycare, there’s always someone around to supervise.
I’ve never experienced any kids with bad behaviour in daycare.
Synthetic - Prompted
I figured a daycare center with multiple staff would be safer because others can monitor and prevent bad behavior.
I figured one bad apple could cause harm with no others to supervise.
Synthetic - LoRA
I always thought that there were less chances of something happening in a day care because there are other people watching.
I thought the chances of something happening were high.
Table 2: Synthetic triplet examples vs annotations (English).
Figure 4: Synthetic Turkish data produced via ICL-Prompting. Unintended code switching and poor intellegibility are apparent throughout.
Figure 5: Lexical overlap between the anchor and positive/negative pairs computed via Dice coefficient. English results, including gold human annotations, are shown on the left. Right compares adapter composition with prompted data in low resource languages. XL-LoRA is excluded as languages differ within the triplet.
Figure 6: Examples of data synthesized by the XL-LoRA generator when trained on machine-translated (MT) and human-translated plus synthesised (HT+Syn) data. MT data shows leads to lower quality.
Figure 7: Alignment and Uniformity values of finetuned embedding models, based on the corresponding STR language embeddings 4 4 4 Alignment and uniformity are computed per language from the STS test set, using sentence pairs with normalized similarity ≥0.8 as positives and all test sentences to estimate the data distribution. . Lower ℓalign values indicate that similar sentences are clustered closely together in the embedding space, while lower ℓuniform values indicate a more evenly distributed embedding space, reducing anisotropy. Here mmBERT is used as the base encoder, but trends are consistent across backbones (see A.10 )
10k
20k
hin
79.5 ± 0.4
80.0 ± 0.1
mar
84.6 ± 0.3
83.9 ± 0.1
tel
83.5 ± 0.3
84.9 ± 0.6
hau
56.1 ± 1.5
59.3 ± 0.9
avg
75.9 ± 0.5
77.0 ± 0.2
Table 3: STS results (mean ± std over 4 seeds, Spearman’s correlation) for XL-LoRA method (mmBERT as the base encoder) trained with 10k vs. 20k data.
Appendix figures & tables23 assets
Supplementary material from the paper’s appendix.
Appendix
Base Encoder
Base Model Description
Synthesised Data Generation Method
STS-B
RoBERTa Base
unsupervised SimCSE
–
80.0
supervised-SimCSE on annotated English triplets
–
85.4
supervised SimCSE
SynCSE-partial (GPT3.5)
83.3
SynCSE-partial (Gemma3-27b)*
83.1
LoRA TA (Gemma3-1b)*
83.2
LoRA TA (Gemma3-27b)*
84.3
Appendix
Table 4: STS-B performance (Spearman’s correlation) of SimCSE-based English models. Results are reproduced via SimCSE fine-tuning methodologies, using their hyperparameter settings. * denotes synthesised data. Original scores for unsupervised SimCSE, supervised SimCSE, and SynCSE-partial (GPT-3.5) are 80.2, 85.8, and 83.9 ( Gao et al., 2021 ; Zhang et al., 2023b ) .
Pooler Type
STR
Afr
Hin
cls + mlp
77.9
81.8
avg
77.6
81.3
afl
78.4
82.0
at2
78.0
81.6
cbp
77.7
81.8
Appendix
Table 5: Spearman correlations for STR performance fine-tuned with Prompting synthesis method in Afrikaans and Hindi, using different pooler types
Batch Size
MLM Obj
STR
Afr
Hin
128
FALSE
78.4
82.0
128
TRUE
78.5
82.1
512
FALSE
79.0
82.8
Appendix
Table 6: Spearman correlations for STR performance fine-tuned with Prompting synthesis method in Afrikaans and Hindi, using different batch sizes and MLM objective.
Figure 8: The prompting strategy for localised SynCSE-partial. As in the original method, each prompt includes five randomly selected examples from a pool of 18, together with a randomly chosen opening sentence from one of the four prompt types shown in Figure 9 . Language specific details are added in the closing prompt.
Figure 9: Positive and hard negative prompts used in the SynCSE-partial methodology ( Zhang et al., 2023b ) to promote diversity in data synthesis.
Task Adapter
Adapter Composition Method
XNLI Accuracy Score
XLM-R
Gemma3-1b
Base model
–
33.3
35.3
Hindi XNLI
–
57.2
65.7
English XNLI
–
56.8
65.3
English XNLI
AdaMergeX with Hindi LA & English LA
60.5
65.8
Appendix
Table 7: XNLI accuracy on the Hindi test set for Base models, LoRA task adapters (TAs) in Hindi and English, and the AdaMergeX cross-lingual TA.
Data Synthesis Method
STR (Hindi)
Gemma3-1b
Gemma3-27b
Base
79.1
81.0
LoRA TA trained on English data
80.2
82.5
Crosslingual TA (Hindi) via Adamergex
80.5
82.7
Appendix
Table 8: Spearman correlations for STR performance in Hindi, using different data synthesis methods with 50,000 synthesized samples.
TA Adapter Specs
LA Adapter Specs
STR (Hindi)
Trained a combined model with both negative and positive prompt examples
Aya annotated dataset
81.1
Combined sentence corpora
82.0
Individual sentences
81.8
Aya annotated + collections dataset
82.4
Trained two individual models with negative and positive prompt examples
Aya annotated dataset
82.5
Combined sentence corpora
83.0
Appendix
Table 9: Spearman correlations for STR performance in Hindi, using different language adapter (LA) and task adapter (TA) specifications with 50,000 synthesized data samples. Aya annotated dataset contains the human annotated samples ( Singh et al., 2024 ) , collections dataset denotes the Aya collections of machine translated samples. Combined sentence corpora and individual sentences experiments source the multilingual corpora from Opper and Siddharth (2025)
LA Adapter Specs
STR
Hindi
Telugu
Afrikaans
Aya annotated dataset
82.2
81.0
–
Combined sentence corpora
82.7
81.4
77.4
Aya annotated + collections dataset
83.0
81.3
77.5
Appendix
Table 10: Spearman correlations for STR performance across Hindi, Telugu, and Afrikaans for different language adapter (LA) and task adapter (TA) specifications synthesising the full dataset. Data for Afrikaans in the Aya annotated category was unavailable.
STR
Hindi
Telugu
Afrikaans
Rank 4
82.1
81.7
77.0
Rank 8
83.0
81.3
77.5
Rank 16
82.4
81.9
77.4
Appendix
Table 11: Spearman correlations for STR performance across Hindi, Telugu, and Afrikaans for different ranks synthesising the full dataset.
Figure 10: Accuracy for XNLI (dev) and STR (dev) performances across different lambdas.
XLM-R
mmBERT
Score
Method
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Afr
Hin
Mar
Tel
Ind
Hau
Kor
MT
80.0
78.2
83.6
84.7
48.3
61.0
73.9
80.5
79.8
83.9
83.1
50.7
59.4
74.1
72.9
HT + MT
80.2
78.4
83.5
84.1
49.3
60.7
72.9
80.7
79.8
84.5
84.6
51.7
59.1
72.7
73.0
HT + Syn
81.2
77.8
84.0
84.0
47.8
58.0
72.9
80.6
79.5
85.0
83.7
48.9
57.7
72.9
72.4
Appendix
Table 12: STR results on synthesised data methods using XL-LoRA models trained on machine-translated (MT), human-translated plus machine-translated (HT+MT) and human-translated plus synthesised (HT+Syn) data.
nDCG@10
Recall@10
XLM-R
mmBERT
Score
XLM-R
mmBERT
Score
Method
Hin
Tel
Ind
Kor
Hin
Tel
Ind
Kor
Hin
Tel
Ind
Kor
Hin
Tel
Ind
Kor
MT
17.2
13.4
14.3
25.4
16.2
8.1
18.7
26.3
17.5
26.9
22.4
21.4
35.9
23.4
14.3
25.8
35.8
25.7
HT + MT
18.2
16.6
17.1
25.2
18.3
11.9
19.0
28.9
19.4
29.3
26.4
24.2
34.6
27.1
20.1
25.7
37.7
28.1
HT + Syn
18.8
16.7
18.1
25.9
20.8
11.6
22.5
26.9
20.2
28.4
28.0
25.2
37.1
29.3
19.4
29.8
36.2
29.2
Appendix
Table 13: MIRACL Retrieval Hard Negative results on synthesised data methods (XL-LoRA; MT vs. HT+MT vs. HT+Syn)
nDCG@10
Recall@10
XLM-R
mmBERT
Score
XLM-R
mmBERT
Score
Method
Hin
Mar
Tel
Hin
Mar
Tel
Hin
Mar
Tel
Hin
Mar
Tel
MT
49.9
56.8
54.2
46.6
55.7
49.5
52.1
69.4
75.0
74.6
65.2
74.3
67.8
71.1
HT + MT
50.2
57.5
54.9
48.2
56.2
51.1
53.0
68.7
75.3
74.7
67.2
75.0
68.9
71.6
HT + Syn
51.2
57.6
55.1
48.8
58.6
51.6
53.8
70.6
75.8
75.4
68.2
76.8
69.7
72.8
Appendix
Table 14: Indic QA Retrieval results on synthesised data (XL-LoRA; MT vs. HT+MT vs. HT+Syn).
nDCG@10
XLM-R
mmBERT
Score
Method
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Afr
Hin
Mar
Tel
Ind
Hau
Kor
MT
76.8
68.2
69.6
63.6
77.7
65.4
75.4
78.7
69.4
70.5
65.7
82.4
66.3
79.1
72.1
HT + MT
78.0
70.1
71.8
64.4
78.9
64.6
76.3
81.1
70.8
72.6
65.6
82.0
62.3
80.4
72.8
HT + Syn
79.2
70.1
71.6
64.6
79.1
65.8
78.4
81.9
70.8
73.9
65.5
83.7
58.9
81.0
73.2
Appendix
Table 15: Belebele Retrieval nDCG@10 results on synthesised data (XL-LoRA; MT vs. HT+MT vs. HT+Syn)
Recall@10
XLM-R
mmBERT
Score
Method
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Afr
Hin
Mar
Tel
Ind
Hau
Kor
MT
88.9
84.1
84.6
80.1
90.1
79.0
89.4
90.4
86.1
85.3
80.6
93.4
79.8
91.8
86.0
HT + MT
90.1
84.7
86.8
81.1
91.0
79.1
89.7
92.6
85.2
86.4
80.2
93.0
79.2
92.1
86.5
HT + Syn
91.1
84.8
87.0
80.2
91.9
80.1
91.6
92.7
86.3
87.8
81.2
94.0
74.2
93.3
86.9
Appendix
Table 16: Belebele Retrieval Recall@10 results on synthesised data (XL-LoRA; MT vs. HT+MT vs. HT+Syn)
nDCG@10
Recall@10
XLM-R
mmBERT
Score
XLM-R
mmBERT
Score
Method
Hin
Tel
Ind
Kor
Hin
Tel
Ind
Kor
Hin
Tel
Ind
Kor
Hin
Tel
Ind
Kor
Base Encoder
1.4
0.6
0.3
4.9
0.3
0.0
0.0
0.7
1.0
1.7
0.7
0.6
6.6
0.4
0.0
0.1
0.7
1.4
Unsupervised
16.1
11.0
8.6
22.7
2.2
0.7
3.3
7.7
9.0
23.5
17.6
12.1
29.1
3.8
1.0
5.2
12.1
13.1
Cross Lingual
19.8
13.3
16.5
27.4
22.0
8.2
20.0
28.3
19.4
29.8
22.0
23.9
36.3
30.6
13.6
27.7
37.5
27.7
Synth - Prompting
16.7
16.3
15.1
21.6
9.5
11.4
9.7
24.5
15.6
24.5
28.8
21.6
32.5
13.6
20.2
14.5
36.6
24.0
Appendix
Table 17: MIRACL Retrieval Hard Negative results across languages.
nDCG@10
Recall@10
XLM-R
mmBERT
Score
XLM-R
mmBERT
Score
Method
Hin
Mar
Tel
Hin
Mar
Tel
Hin
Mar
Tel
Hin
Mar
Tel
Base Encoder
5.9
21.0
21.7
1.9
2.0
39.6
15.4
12.2
31.1
43.1
4.3
4.6
57.2
25.4
Unsupervised
43.2
44.6
48.2
17.1
23.1
13.9
31.7
61.9
62.8
67.2
31.5
38.7
24.2
47.7
Cross Lingual
50.7
55.0
50.8
46.2
50.1
39.6
48.7
70.0
73.4
69.6
64.9
68.3
57.2
67.2
Synth - Prompting
52.3
52.3
51.8
44.4
47.8
42.5
48.5
72.0
71.7
72.1
62.9
67.0
59.9
67.6
Appendix
Table 18: Indic QA Retrieval results across languages
nDCG@10
XLM-R
mmBERT
Score
Method
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Base Encoder
14.7
11.5
13.8
14.8
27.9
5.9
23.0
1.1
0.8
0.9
1.0
1.1
1.2
1.2
8.5
Unsupervised
7.4
8.0
5.7
49.7
66.5
18.6
62.4
36.1
20.1
16.8
12.5
54.4
5.0
32.1
28.2
Cross Lingual
74.9
65.6
66.8
60.2
79.1
41.9
74.3
78.5
64.7
63.0
48.0
82.9
30.0
77.4
64.8
Synth - Prompting
70.5
58.5
61.0
56.6
71.0
48.3
72.7
65.0
53.6
53.5
48.7
73.2
28.0
70.9
59.4
Synth - Adapter Composition
77.7
64.0
68.6
61.3
76.9
56.7
73.1
76.6
58.8
61.0
57.6
79.9
43.6
72.7
66.3
Appendix
Table 19: Belebele Retrieval nDCG@10 results across languages
Recall@10
XLM-R
mmBERT
Score
Method
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Afr
Hin
Mar
Tel
Ind
Hau
Kor
Base Encoder
20.8
16.8
20.4
20.9
39.8
10.6
31.9
2.2
1.7
2.0
2.1
2.1
2.4
2.4
12.6
Unsupervised
12.8
13.7
11.2
64.1
81.2
30.0
78.3
52.2
32.0
27.0
22.0
69.2
8.9
47.0
39.3
Cross Lingual
87.4
80.0
83.1
77.1
90.3
54.2
86.9
90.6
78.7
78.1
62.8
92.7
37.3
90.7
77.9
Synth - Prompting
84.1
73.4
77.3
71.7
84.6
63.8
85.9
81.1
69.6
70.8
64.9
86.6
40.9
84.4
74.2
Synth - Adapter Composition
89.1
78.2
83.8
75.7
89.3
72.4
85.9
90.4
75.6
76.6
72.4
90.7
58.8
85.1
80.3
Appendix
Table 20: Belebele Retrieval Recall@10 results across languages
Prompting Strategy
Zero-Shot Prompt
Huang et al. (2023) Prompting – XNLI Classification
I want you to act as a natural language inference expert for {language}. Premise: {premise}. Hypothesis: {hypothesis}. You should retell the premise and hypothesis in English. You should judge whether the hypothesis is true (entailment), false (contradiction), or undetermined (neutral) given the premise. The relationship can be chosen from entailment, contradiction and neutral. You should step-by-step answer the request. You should tell me the relationship in this format ‘Relationship:’.
You are an expert at natural language inference. Given a premise and hypothesis (in {language}), you should return an integer classification. The options are as follows: 0 for entailment, 1 for neutral, and 2 for contradiction. Return only the integer without any preamble or explanation. Premise: {premise}. Hypothesis: {hypothesis}.
Prompting – Positive Pair Generation (This Work)
You are an expert at natural language inference. Given a premise, you should return an entailment sentence example (in {language}) to the premise. Return only the entailment sentence example without any preamble or explanation. Premise: {premise}.
Prompting – Negative Pair Generation (This Work)
You are an expert at natural language inference. Given a premise, you should return a contradiction sentence example (in {language}) to the premise. Return only the contradiction sentence example without any preamble or explanation. Premise: {premise}.
Appendix
Table 21: Zero-shot prompting strategies used in this study.
Figure 11: Qualitative review comparing the Turkish semi annotated data ( Halat and Atlamaz, 2024 ) , synthetic data via Prompted, Adapter Composition and XL-LoRA methods. We constructed the annotated triplet dataset from the ImplicaTR dataset ( Halat and Atlamaz, 2024 ) by treating entailment pairs as positive examples and contradiction pairs as hard negatives.
Figure 12: Alignment and Uniformity analysis of XLM-R based fine tuned sentence embedding models, based on Telugu STR language embeddings.
Low-resource languages (LRLs) often lack high-quality, large-scale datasets for training effective text embedding models, hindering their application in tasks like retrieval-augmented generation (RAG) and semantic search. In this work, we challenge the prevailing assumption that effective semantic alignment requires massive datasets or pristine, human-verified translations. Focusing on Armenian (an LRL with a unique script), we introduce a cost-effective adaptation strategy using small scale noisy synthetic data generated by translating English Reddit title-body pairs with open-weights models. We establish a comprehensive evaluation benchmark comprising existing datasets, translated data, and a manually curated dataset. Our experiments reveal a surprising "Less is More" phenomenon: fine-tuning a multilingual encoder (mE5) on just 10,000 noisy synthetic pairs yields 11-12% average improvements across the benchmark with a 20%+ relative improvement in retrieval performance, matching the performance of models trained on ~1 million examples. Furthermore, we demonstrate that neither increasing data scale, improving translation quality via state-of-the-art LLMs, nor diversifying data domains yields significant gains over this minimal baseline. We validate the generalizability of these findings on another LRL with a unique script. Our results suggest that semantic alignment for LRLs saturates early and is highly robust to noise, democratizing high-performance embedding creation for resource-constrained communities. We release the model, data, and the benchmark at https://metric-ai-lab.github.io/less-is-more-embeddings/ to facilitate further research.
We present F2LLM-v2, a new family of general-purpose, multilingual embedding models in 8 distinct sizes ranging from 80M to 14B. Trained on a newly curated composite of 60 million publicly available high-quality data samples, F2LLM-v2 supports more than 200 languages, with a particular emphasis on previously underserved mid- and low-resource languages. By integrating a two-stage LLM-based embedding training pipeline with matryoshka learning, model pruning, and knowledge distillation techniques, we present models that are far more efficient than previous LLM-based embedding models while retaining competitive performances. Extensive evaluations confirm that F2LLM-v2-14B ranks first on 11 MTEB benchmarks, while the smaller models in the family also set a new state of the art for resource-constrained applications. To facilitate open-source embedding model research, we release all models, data, code, and intermediate checkpoints.
Large language models (LLMs) have become an essential tool for natural language processing and artificial intelligence in general. Current open-source models are primarily trained on English texts, resulting in poorer performance on less-resourced languages and cultures. We present a set of methodological approaches necessary for the successful adaptation of an LLM to a less-resourced language, and demonstrate them using the Slovene language. We present GaMS3-12B, a generative model for Slovene with 12 billion parameters, and demonstrate that it is the best-performing open-source model for Slovene within its parameter range. We adapted the model to the Slovene language using three-stage continual pre-training of the Gemma 3 model, followed by two-stage supervised fine-tuning (SFT). We trained the model on a combination of 140B Slovene, English, Bosnian, Serbian, and Croatian pretraining tokens, and over 200 thousand English and Slovene SFT examples. We evaluate GaMS3-12B on the Slovenian-LLM-Eval datasets, English-to-Slovene translation, and the Slovene LLM arena. We show that the described model outperforms 12B Gemma 3 across all three scenarios and performs comparably to much larger commercial GPT-4o in the Slovene LLM arena, achieving a win rate of over 60 %.
Domen Vreš, Tjaša Arčon, Timotej Petrič +3
University of Ljubljana, Faculty of Computer and Information Science, Ljubljana, Slovenia