Sheet superconductivity in : crystal structure of the tetragonal matrix

Sheet conductivity was found in oxygen reduced . The sheets are aligned along the twin boundaries of the unreduced starting material . The bulk transforms during the oxygen loss to a phase with tetragonal crystal structure. The space group is with lattice parameters a = 0.739 nm and c = 0.388 nm. The perovskite-like structure contains distorted octahedra with W - O distances between 0.17 nm and 0.218 nm.