Low Field Scaling of the Flux-Flow Resistivity in the Unconventional SuperconductorUPt3

Measurements of the flux-flow resistivity in the unconventional superconductor ${\mathrm{UPt}}_3$ are reported for a large range of magnetic field. In agreement with a recent theory, ${\rho }_f$ at low field is far larger than that found in conventional superconductors. Its field dependence at different temperatures shows a predicted scaling relation for clean superconductors. The crossover from localized to delocalized quasiparticle excitations around the vortex is also observed as the magnetic field increases.