A new langbeinite-type phosphate: K(2)AlSn(PO(4))(3).

Single crystals of the title compound, dipotassium aluminium tin(IV) tris-[phosphate(V)], K(2)AlSn(PO(4))(3), were synthesized by a high temperature reaction in a platinum crucible. In the structure, the Al(III) and Sn(IV) atoms occupy the same site on a threefold rotation axis with occupational disorder in a 1:1 ratio. In the three-dimensional structure, Al/SnO(6) octa-hedra and PO(4) tetra-hedra are inter-connected via their vertices, yielding a [Al/SnP(3)O(12)](n) framework. The K atoms (site symmetry 3) reside in the large cavities delimited by the [Al/SnP(3)O(12)](n) framework, and are surrounded by 12 O atoms.