Chemical preparation, X-ray single-crystal, thermal behavior, and IR spectroscopy investigations are given for a new organic cation dihydrogenomonophosphate (C6H8N3O)(2)(H2PO4)(2) (denoted IAHP) in the solid state. This compound crystallizes in the orthorhombic space group P2(1)2(1)2(1). The unit cell dimensions are: a = 7.422(3) angstrom, b = 12.568(5) angstrom, c = 20.059(8) angstrom with V = 1871.1(13) angstrom(3) and Z = 4. The structure has been solved using direct method and refined to a reliability R factor of 0.029. The atomic arrangement can be described as inorganic layers of H2PO4- anions between which are located the organic groups (C6H8N3O)(+) through multiple hydrogen bonds. (C) 2006 Elsevier Ltd. All rights reserved.