Synthesis and Physical Properties of the New Oxybismuthides BaTi2Bi2O and (SrF)2Ti2Bi2O with ad1Square Net

We have recently reported the d(1) square-lattice compound BaTi(2)Sb(2)O, which shows superconductivity at T(c) = 1.2K coexisting with a charge- or spin-density wave (CDW/SDW) state. Here, we successfully prepared two new oxybismuthides, BaTi(2)Bi(2)O and (SrF)(2)Ti(2)Bi(2)O, as the first Pn = Bi compounds in the ATi(2)Pn(2)O family. The CDW/SDW state disappeared for both compounds, presumably owing to the considerable interaction between the Ti-3d and Bi-6s orbitals. The complete suppression of the CDW/SDW instability resulted in an enhanced T(c) of 4.6 K for BaTi(2)Bi(2)O. However, (SrF)(2)Ti(2)Bi(2)O exhibits no superconductivity, suggesting the importance of the interlayer interaction for superconductivity.