  We describe three previously unreported superconductors, BaPb3,
Ba0.89Sr0.11Pb3 and Ba0.5Sr0.5Pb3. 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 (Tc) are similar for all - 2.2 K for
BaPb3, 2.7 K for Ba0.89Sr0.11Pb3 and 2.6 K for Ba0.5Sr0.5Pb3, and the
previously reported Tc of SrPb3, ~ 2 K, 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.
