Thermal conductivity of superconducting alloys with paramagnetic admixture at an electronic topological transition

The electronic thermal conductivity $K^s$ is calculated in superconducting alloys with paramagnetic impurity when there are singularities in the electron energy spectrum of the alloys. An electronic topological transition with the “creation” of a fiat section on the Fermi surface is considered, and the dependence of the order parameter $\Delta$ and the ratio $K^s/K_n$ on the pressure, temperature, and concentration of the magnetic admixture is studied. In particular, an anomalous dependence of the ratio $K^s/K_n$ on the pressure is obtained: Near the critical pressure, $K^s/K_n$ has a minimum, the depth of which depends on the concentration of the magnetic admixture.