Single crystals of the solid solution iron aluminium tris(dihydrogenphosphate), (Fe(0.81)Al(0.19))(H(2)PO(4))(3), have been prepared under hydrothermal conditions. The compound is a new monoclinic variety (gamma-form) of iron aluminium phosphate (Fe,Al)(H(2)PO(4))(3). The structure is based on a two-dimensional framework of distorted corner-sharing MO(6) (M = Fe, Al) polyhedra sharing corners with PO(4) tetrahedra. Strong hydrogen bonds between the OH groups of the H(2)PO(4) tetrahedra and the O atoms help to consolidate the crystal structure.