Structure and superconductivity of BaBiO3 doped with alkali ions

XRD shows that doping BaBiO3 with alkali ions transforms the larger monoclinic parent lattice into a more compact cubic or nearly cubic lattice. This lattice contraction favors the transition from semiconductor to metal. It leads also to superconductivity. Doping BaBiO3 with both K and Rb raises the onset resistivity Tc above those obtained by doping with either K or Rb.