We report measurements of the microwave complex resistivity at 48 GHz in SmBa2 Cu3 O7−δ thin
films. Measurements are performed with a moderate magnetic field, μ0H < 0.8T, applied along the
c-axis. We find that the complex resistivity presents clear sublinear field dependences, and that the
imaginary part is remarkably sensitive to the moderate magnetic field. Interpretation considering
an unusually strong pinning leads to very anomalous field dependences of the single-vortex viscosity
and of the pinning constant. By contrast, allowing for a significant effect of the magnetic field on
the depletion of the condensate, the data are quantitatively described by the simple free-flow-like
expression, supplemented with two-fluid conductivity. In this frame, we obtain the vortex viscosity
from the data. We compare vortex viscosity in SmBa2Cu3 O7−δ and in YBa 2 Cu3 O7−δ
