Electronic properties of the half-Heusler compounds Co1-xFexTiSb -: art. no. 041101

We report on de transport and optical investigations of single crystals of the title compounds with x = 0, 0.015, and 0.05. For x = 0, both the resistivity and the optical properties exhibit a metalliclike behavior. With decreasing temperature we note a considerable shift of spectral weight from energies above 700 cm(-1) into the far infrared range of the optical spectra. For 1.5% and 5% Fe doping the low-temperature resistivity is enhanced and the optical spectra are typical for insulators. Our data are in conflict with recent experimental results on polycrystalline samples and are related to issues raised by band-structure calculations.