The iron phosphate, Fe(H2PO4)(3), was synthesized through a precipitation route by means of acidic media. As the compound is highly hygroscopic, the structure was solved ab initio by powder X-ray diffraction under nitrogen flow at room temperature and 200 degrees C. This phase is antiferromagnetic below 30 K. It converts into Fe(PO3)(3) at 550 degrees C, after dehydration. Electrochemical characterizations, performed on the last compound, show irreversible decomposition into metallic iron. (c) 2005 Elsevier Ltd. All rights reserved.