  We want to develop spectral diagnostics of stellar populations in the
near-infrared (NIR), for unresolved stellar populations. We created a
semi-empirical population model and we compare the model output with the
observed spectra of a sample of elliptical and bulge-dominated galaxies that
have reliable Lick-indices from literature to test if the correlation between
Mg2 and CO 1.62 micron remains valid in galaxies and to calibrate it as an
abundance indicator. We find that (i) there are no significant correlations
between any NIR feature and the optical Mg2; (ii) the CaI, NaI and CO trace the
alpha-enhancement; and (iii) the NIR absorption features are not influenced by
the galaxy's age.
