OPTICAL MEASUREMENTS AND BAND CALCULATIONS OF FESI

Reflectivity measurements of high quality FeSi single crystal have bee n performed at 6 and 300 K over a very wide spectral region from 0.05 to 30 eV. The optical conductivity is obtained by a Kramers-Kronig tra nsformation, and it is discussed in connection with the recent band ca lculation in which the relativistic spin-orbit effects are taken into account and with other measurements done on FeSi before. The result of direct photoconductivity measurement in the spectral region from 200 to 800 cm(-1) is also presented.