  We introduce Latxa, a family of large language models for Basque ranging from
7 to 70 billion parameters. Latxa is based on Llama 2, which we continue
pretraining on a new Basque corpus comprising 4.3M documents and 4.2B tokens.
Addressing the scarcity of high-quality benchmarks for Basque, we further
introduce 4 multiple choice evaluation datasets: EusProficiency, comprising
5,169 questions from official language proficiency exams; EusReading,
comprising 352 reading comprehension questions; EusTrivia, comprising 1,715
trivia questions from 5 knowledge areas; and EusExams, comprising 16,774
questions from public examinations. In our extensive evaluation, Latxa
outperforms all previous open models we compare to by a large margin. In
addition, it is competitive with GPT-4 Turbo in language proficiency and
understanding, despite lagging behind in reading comprehension and
knowledge-intensive tasks. Both the Latxa family of models, as well as our new
pretraining corpora and evaluation datasets, are publicly available under open
licenses at https://github.com/hitz-zentroa/latxa. Our suite enables
reproducible research on methods to build LLMs for low-resource languages.
