Anomalous Thermal Conductivity of Semi-Metallic Superconductors with Electron-Hole Compensation

The effects of low carrier density and carrier compensation on mixed-state thermal transport are investigated beyond the quasiclassical approximation. It is shown that, contrary to the usual observations, the interplay of the two effects leads to an {\it increase} in the thermal conductivity immediately below the upper critical field $H_{c2}$. Our result can account for the anomalous behavior of the mixed-state thermal conductivity near $H_{c2}$ recently observed in URu$_2$Si$_2$.