Metal-insulator transitions in the kondo insulator FeSi and classic semiconductors are similar

We have observed the metal-insulator transition in the strongly correlated insulator FeSi with the chemical substitution of Al at the Si site. The magnetic susceptibility, heat capacity, and field-dependent conductivity are measured for Al concentrations ranging from 0 to 0.08. For concentrations greater than or equal to 0.01 we find metallic properties quantitatively similar to those measured in Si:P with the exception of a greatly enhanced quasiparticle mass. Below 2 K the temperature and field-dependent conductivity can be completely described by the theory of disordered Fermi liquids.