García Pérez, A.E.Sánchez Blázquez, PatriciaVazdekis, A.Allende Prieto, C.Milone, A. de C.Sansom, A.E.Gorgas García, Francisco JavierFlacon-Barroso, J.Martín Navarro, I.Cacho, R.2023-06-162023-06-162021-080035-871110.1093/mnras/stab076https://hdl.handle.net/20.500.14352/4463© 2021 The Author(s). We thank the referee for a thorough revision that helped us to improve the original draft and the presentation of this work. We are also grateful to E. Marmol-Queralt ´ o for helping us during ´ the observations and to R. Peletier for useful discussions. AEGP, AV, PSB, and JG acknowledge financial support from the coordinated grants AYA2016-77237-C3-1-P, AYA2016-77237-C3-2-P, PID2019-107427GB-C32 and PID2019-107427GB-C31 from the Spanish Ministry of Science, Innovation and Universities (MCIU), while CAP does from AYA2017-86389 (also from the MCIU). ACM was supported by the research grant (309562/2015-5) from the Brazilian National Council for Scientific and Technological Development (CNPq) foundation. He also thanks the Institutional Training Program (PCI) of the Brazilian Ministry of Science, Technology and Innovations (MCTI) at Instituto Nacional de Pesquisas Espaciais (INPE) (individual process 17.0018/2010-5 under the institutional process 680.006/2009-5) for financial support for the 2011 (run A) observational campaign.Extragalactic astronomy and stellar astrophysics are intrinsically related. In fact, the determination of important galaxy properties such as stellar masses, star formation histories, or chemical abundances relies on the ability to model their stellar populations. One important ingredient of these models is stellar libraries. Empirical libraries must have a good coverage of T_(eff), [Z/H], and surface gravity, and have these parameters reliably determined. MILES is one of the most widely used empirical libraries. Here, we present an extension of this library with 205 new stars especially selected to cover important regions of the parameter space, including metal-poor stars down to [Fe/H] ∼ −1.0. We describe the observations and data reductions as well as a new determination of the stellar parameters, including [α/Fe] ratio. The new MILES library contains 1070 stars with homogeneous and reliable determination of [Fe/H], T_(eff), log g, and [α/Fe] ratio.engjournal articlehttp://dx.doi.org/10.1093/mnras/stab076https://academic.oup.com/open access52Stellar population synthesisEvolutionary synthesisMain-sequencesElemental abundancesChemical abundancesSpectral libraryData releaseStarsCatalogSolarFísica atmosférica2501 Ciencias de la Atmósfera