Electron Tunneling Experiments on AmorphousGe1−xAux

Tunneling measurements of the electronic density of states of amorphous ${\mathrm{Ge}}_{1-x}{\mathrm{Au}}_x$ near the metal-insulator transition at $x=0.12\mathrm{}$ are reported. In the metallic phase there is a giant zero-bias anomaly with a minimum in the density of states at the Fermi energy. In the insulating phase a pseudogap opens, centered about the Fermi energy, with zero density of states at the Fermi energy.