“…These titanium pnictide oxides BaTi 2 Pn 2 O (Pn = Sb, Bi) consist of superconducting Ti 2 Pn 2 O layers and Ba blocking layers. At present, eight titanium pnictide oxides Na 2 Ti 2 Pn 2 O (Pn = As, Sb), (SrF) 2 Ti 2 Pn 2 O (Pn = As, Sb, Bi), and BaTi 2 Pn 2 O (Pn = As, Sb, Bi) have been synthesized, but only BaTi 2 Pn 2 O (Pn = Sb, Bi) shows superconductivity [11,[14][15][16][17]. Though BaTi 2 Pn 2 O is not high-T c superconductor, several unique and attracting physical properties have been found: two superconducting domes in the phase diagram of isovalent solid solutions of BaTi 2 (Sb 1-x Bi x ) 2 O and unconventional DW instability [18,19].…”