Flux flow and fluctuation resistivity at 48 GHz in high-T-c superconductors

We present measurements of the real part of the microwave restitivity at 48 GHz in YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+x films, as a function of the tem perature and of the static magnetic field. In zero field, the resistivity a bove the critical temperature is well described by the frequency-dependent fluctuational excess conductivity. In a static magnetic field and below T-c , the resistivity in YBa2Cu3O7-delta can Be fully described by a simple flu x-flow: model, while in Bi2Sr2CaCu2O8+x this model applies only partially. We discuss possible alternative models.