A family of Pb-based superconductors with variable cubic to hexagonal packing

We describe three previously unreported superconductors, BaPb₃, Ba_0.89Sr_0.11Pb₃, and Ba_0.5Sr_0.5Pb₃. These three materials, together with SrPb₃, form a distinctive isoelectronic family of intermetallic superconductors based on the stacking of Pb planes, with crystal structures that display a hexagonal to cubic perovskite-like progression, as rarely seen in metals. The superconducting transition temperatures (T_c) are similar for all -2.2K for BaPb₃, 2.7K for Ba_0.89Sr_0.11-Pb₃, and 2.6K for Ba_0.5Sr_0.5Pb₃, and the previously reported T_c of SrPb₃, ∼2K, is confirmed. The materials are moderate coupling superconductors, and calculations show that the electronic densities of states at the Fermi energy are primarily contributed by Pb. The observations suggest that the Pb-stacking variation has only a minor effect on the superconductivity.