Composition-induced structural instability and strong-coupling superconductivity in Au_1-xPd_xTe₂

The physical properties and structural evolution of the MX₂-type solid solution Au_1-xPd_xTe₂are reported. The end member AuTe2 is a normal metal with a monoclinic distorted CdI₂-type structure with preformed Te-Te dimers. A monoclinic-trigonal structural phase transition at a finite temperature occurs upon Pd substitution and is suppressed to zero temperature near x = 0.55, and a superconducting phase with a maximum T_c= 4.65 K emerges. A clear indication of strong coupling superconductivity is observed near the composition of the structural instability. The competitive relationship between Te-Te dimers and superconductivity is proposed.