We have entered an era of large spectroscopic surveys in which we can measure, through automated pipelines, the atmospheric parameters and chemical abundances for large numbers of stars. Calibrating these survey pipelines using a set of "benchmark stars" in order to evaluate the accuracy and precision of the provided parameters and abundances is of utmost importance. The recent proposed set of Gaia FGK benchmark stars has up to five metal-poor stars but no recommended stars within -2.0<[Fe/H]<-1.0dex. However, this metallicity regime is critical to calibrate properly. In this paper, we aim to add candidate Gaia benchmark stars inside of this metal-poor gap. We began with a sample of 21 metal-poor stars which was reduced to 10 stars by requiring accurate photometry and parallaxes, and high-resolution archival spectra. The procedure used to determine the stellar parameters was similar to the previous works in this series for consistency. The difference was to homogeneously determine the angular diameter and effective temperature (Teff) of all of our stars using the Infrared Flux Method utilizing multi-band photometry. The surface gravity (logg) was determined through fitting stellar evolutionary tracks. The [Fe/H] was determined using four different spectroscopic methods fixing the Teff and logg from the values determined independent of spectroscopy.

Cone search capability for table J/A+A/592/A70/sources (General information on metal-poor benchmark candidates selected (from table 1 of the paper))