A new layered ammonium cobalt-zinc phosphate has been synthesized under solvothermal conditions at 160℃ and the structure solved using room-temperature single-crystal X-ray diffraction data. (NH4[Zn2-xCox(PO4)(HPO4)] (x 0.12), Mr) 339.75, triclinic, space group P-1, a) 5.237(1) Å, b) 8.949(1) Å3, c) 9.728(1) Å, R) 74.99(1)°, â) 77.64(1)°, ç) 72.92(1)°, V) 416.19(1) Å3, Z) 2, 1511 observed data measured with I > 3ó(I), R) 4.31% and Rw) 4.67%). The structure consists of MO4 (M) Zn, Co), PO4, and PO3(OH) tetrahedra linked to form buckled layers containing three-and four-membered rings between which ammonium cations reside. A network of hydrogen bonds involving both interlayer and layer-toammonium interactions holds the phosphate layers together.