Microwave resistance measurements which were undertaken to seek direct evidence for the existence of the mixed state in thin type-I films are described. The measurements were for the most part confined to indium films. The observed change in the microwave resistance of the films as a function of magnetic field applied perpendicular to the surface is, in detail, similar to reported surface resistance measurements on bulk type-II superconductors. This includes the intrinsic hysteresis observed below $H_{c2\mathrm{}}$ and the existence of a superconducting surface layer at the edge of the film which presists to $H_{c3\mathrm{}}$.

• Received 7 April 1967

DOI:https://doi.org/10.1103/PhysRev.161.398