We have built a new grid of synthetic spectra in the wavelength range λλ 4600-5600 Å for [α-elements/Fe] = 0.0, +0.2, +0.4 and +0.6. The Lick indices Mg2, Mgb, Fe5270 and Fe5335 are measured in all grid spectra, and their behaviour with stellar parameters is studied.
For the calculation of this new grid, the set of atomic and molecular constants was revised and model atmospheres with overshooting and mixing length parameters appropriate to reproduce the wings of the Hβ line (suitable to indicate temperatures) were computed. We also present a grid in the wavelength range λλ 6000 – 10200 Å. A computation of a high-resolution grid of spectra in the range λλ 3800–7000 Å, as well as a full grid in the range λλ 3000–10200 Å, to be further used in conjunction with evolutionary population synthesis models, are also underway.