Estimating [α/Fe] from Gaia low-resolution BP/RP spectra using the ExtraTrees algorithm Alvin Gavel, René Andrae, Morgan Fouesneau, Andreas J. Korn and Rosanna Sordo A&A, 656 (2021) A93 Published online: 08 December 2021 DOI: 10.1051/0004-6361/202141589