We present and discuss reflectance and trasmittance measurements on CrSi_2 an FeSi_2 polycristalline films, The strong and sharp structures observed in the 100-700 cm^-1 wavenumber range are interpreted basin on normal modes symmetry properties. We also examine the optical response in the energy region around the band-gap for CrSi_2 and determine the dispersion of its complex refractive index
