Ca0.81 Cu2 O7 Sr2 Tl1.19 Martin C, Maignan A, Labbe P, Chardon J, Hejtmanek J, Raveau B Chemistry of Materials 7 (1995) 1414-1418 Single-crystal study of the 55 K superconductor Tl Sr2 Ca Cu2 O7-d _cod_database_code 1001666 _database_code_amcsd 0012204 3.7966 3.7966 12.092 90 90 90 P4/mmm atom x y z occ Tl1 .0793 0 0 .25 Ca1 .5 .5 .5 .81 Tl2 .5 .5 .5 .19 Sr1 .5 .5 .2165 Cu1 0 0 .3642 O1 0 .5 .3714 O2 0 0 .166 O3 .5 .5 0