Density of states of amorphous GdxSi1-x at the metal-insulator transition

We have determined the electronic density of states of amorphous Gd xSi (1-x), N(GdSi)(E), in the vicinity of the metal-insulator transition by measuring the tunneling conductance dI/dV across a Gd xSi (1-x)/oxide/Pb tunnel junction at low T (T approximately 100 mK). By applying a magnetic field we can tune through the metal-insulator transition and simultaneously measure the transport and N(E) on a single sample. We find a smooth transition from a metal with strong Coulomb interactions to a developing Coulomb gap in the insulating regime. In the metallic region N(GdSi)(0) scales approximately with sigma(2).