Current-voltage characteristics of superconducting Pb films in contact with a normal metal

We have observed step structure in the current-voltage characteristics of single-crystal and polycrystal Pb films in parallel applied magnetic field near $H_{c2}$ of the film. The single-crystal films are in direct contact with a normal metal which suppresses surface superconductivity on that side of the film. These films exhibit the same type of step structure in their $I-V$ curves as do Pb films deposited directly onto glass substrates.