H-(top) and K-(bottom) band radially binned spectra for the bulge of M31, observed with LUCI@LBT. In each panel, the main absorption features from Eftekhari et al. (2021, hereafter EVL21) are marked with a black arrow. Gray bands mark the sidebands of the CO absorption features analyzed in the present work, from H throughout K band (see the text). Spectra with different colors correspond to different galactocentric distances. The distance to the center along the slit, R, is encoded with colors from blue (the southwest side of the slit) through red (northeast), as shown by the inset colored bar in the bottom panel.