Abstract

Tunneling and optical transmission studies have been performed on superconducting samples of Rb C . At temperatures much below the superconducting transition temperature the energy gap is meV, corresponding to . The low temperature density of states, and the temperature dependence of the optical conductivity resembles the BCS behavior, although there is an enhanced ``normal state" contribution. The results indicate that this fulleride material is an s-wave superconductor, but the superconductivity cannot be described in the weak coupling limit.