Full superconducting gap in the candidate topological superconductor In${}_{1-x}$Pb${}_x$Te for x = 0.2

High-pressure synthesis techniques have allowed for the growth of samples on the indium-rich side of (Pb,In)Te, which have increased superconducting transition temperatures compared to lead-rich compounds. In this study we present measurements of the temperature dependence of the London penetration depth $\mathrm{\Delta }\lambda (T)$ in the compound In${}_{0.8}$Pb${}_{0.2}$Te, which shows a bulk $T_{c,onset}$ of $\sim 4.75$ K. The results indicate fully gapped BCS-like behavior, ruling out odd-parity, topologically nontrivial $A_{2u}$ pairing; however, odd-parity $A_{1u}$ pairing is still possible. Critical field values measured below 1 K and other superconducting parameters are also presented.