We report the discovery of a family of ternary platinum phosphides APt3P (A = Ca, Sr and La), which crystallize in an antiperovskite-based structure closely related to that of the heavy fermion superconductor CePt3Si. All three phosphides showed superconductivity at low temperatures and the highest critical temperature Tc = 8.4 K was observed for SrPt3P. The analysis of specific heat C(T) for SrPt3P shows clear evidence for very strong coupling s-wave superconductivity with a large ratio between superconducting gap D0 and Tc, 2D0/kBTc ~ 5, and the presence of low-energy phonons. The presence of multiple Fermi surface pockets was inferred from the nonlinear magnetic field dependence of Hall resistivity, which we argue might play a role in realizing the strong coupling of charge carriers with the low lying phonons.
@article{arxiv.1205.1589,
title = {Strong coupling superconductivity at 8.4 K in an antiperovskite phosphide SrPt3P},
author = {T. Takayama and K. Kuwano and D. Hirai and Y. Katsura and A. Yamamoto and H. Takagi},
journal= {arXiv preprint arXiv:1205.1589},
year = {2012}
}