Type II superconducting parameters of Tl-doped PbTe determined from heat capacity and electronic transport measurements

Tl-doped PbTe $\left({\mathrm{Pb}}_{1-x}{\mathrm{Tl}}_x\mathrm{Te}\right)$ is an anomalous superconductor with a remarkably high maximum $T_c$ value given its relatively low carrier concentration. Here, we present results of systematic measurements of superconducting parameters for this material, for Tl concentrations up to $x=1.4\%$. We find that it is a type II, weak-coupled BCS superconductor in the dirty limit and discuss implications for the applicability of the charge Kondo model recently proposed to account for superconductivity in this system.