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 $\ge 0.01$ we find metallic properties quantitatively similar to those measured in $\mathrm{S}\mathrm{i}:\mathrm{P}$ 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.