Tetragonality induced superconductivity in anti-ThCrSi-type REOBi (RE = rare earth) with Bi square nets.

We report a series of layered superconductors, anti-ThCrSi-type REOBi (RE = rare earth), composed of electrically conductive Bi square nets and magnetic insulating REO layers. Superconductivity was induced by separating the Bi square nets as a result of excess oxygen incorporation, irrespective of the presence of magnetic ordering in REO layers. Intriguingly, the transition temperature of all REOBi including nonmagnetic YOBi was approximately scaled by unit cell tetragonality (c/a), implying a key role in the relative separation of the Bi square nets to induce superconductivity.