Nonmonotonic magnetic-field dependence and scaling of the thermal conductivity for superconductors with nodes of the order parameter

We show that there is a mechanism for the nonmonotonic behavior of the magnetic-field dependence of the electronic thermal conductivity κ of clean superconductors with nodes of the order parameter on the Fermi surface. In particular, for unitary scatterers the nonmonotony of the relaxation time takes place. A contribution from the intervortex space turns out to be essential for this effect even at low temperatures. Our results are in a qualitative agreement with recent experimental data for superconducting UPt₃. For E₂ᵤ-type pairing we find approximately the scaling of the thermal conductivity in the clean limit with a single parameter x=(T/Tc)√Bc2/B at low fields and low temperatures, as well as a weak low-temperature dependence of the anisotropy ratio κzz/κyy in zero field. For E1g-type pairing deviations from the scaling are more noticeable and the anisotropy ratio is essentially temperature dependent.