Normal-state transport properties (2–300 K) of the polycrystalline series ${\mathrm{Sn}}_{1.03-\delta -x}{\mathrm{In}}_x\mathrm{Te} (0\le x\le 0.07$; $\delta \le 0.0025$) were investigated by means of electrical resistivity, thermopower, Hall effect, and thermal conductivity measurements. The distortion of the valence-band structure by the In-induced resonant level (RL) has a profound influence on the evolution of the normal-state properties with $x$ and on the emergence of superconductivity evidenced by specific-heat measurements down to 0.35 K. In addition to a nearly 40-fold increase in the residual electrical resistivity ${\rho }_0$ on going from $x=0.0$ to 0.05, the thermopower $\alpha$ shows a nonlinear, complex behavior as a function of both temperature and $x$. While Hall measurements indicate a dominant holelike response across the entire composition and temperature ranges, $\alpha$ changes sign below about 100 K and remains negative down to 5 K for $0.0015\le x\le 0.0045$. Additional measurements under magnetic fields ${\mu }_{0}H$ of up to 14 T further shows that $\alpha \left({\mu }_{0}H\right)$ gradually shifts towards positive values, suggestive of a dominant holelike contribution to $\alpha$. Superconductivity emerges for $x=0.02$ at a critical temperature $T_{\mathrm{c}}=0.67$ K, with $T_{\mathrm{c}}$ increasing with $x$ to reach 1.73 K for $x=0.07$. The variations in the superconducting parameters with $x$, notably the specific-heat jump at $T_{\mathrm{c}}$, confirm the results reported in prior studies and suggests a nontrivial role of the RL on the electron-phonon coupling strength. The striking similarities between this series and the canonical resonant system ${\mathrm{Pb}}_{1-x}{\mathrm{Tl}}_x\mathrm{Te}$ provide an excellent experimental opportunity to gain a deeper understanding of the close interplay between resonant level, anomalous transport properties, and superconductivity.

• Received 24 November 2021
• Revised 3 May 2022
• Accepted 5 August 2022

DOI:https://doi.org/10.1103/PhysRevB.106.075205