Superconducting hydrides of PdAlx and PdInx alloys

Ion-implantation studies of Pd-based alloys are presented with emphasis on the superconducting properties of certain metal hydrides. Addition of aluminum to PdH yields an initial small increase in Tc and subsequently lowers Tc rapidly for aluminum content exceeding 10%. Similarly PdInxHy alloys exhibit a decreasing Tc with increasing indium content, in contrast to expectations of existing theories. The role of spin fluctuations, phonon spectra, and hydrogen content are discussed in view of the strong enhancement of Tc in Pd-noble-metal alloy hydrides