The new orthorhombic Fe(AsO4) phase has been synthesized by thermal treatment at 525 degrees C of a new (NH4)[Fe(AsO4)F] compound, with a [Fe(AsO4)F]- skeleton showing channels where the ammonium cations are located. The crystal structure of Fe(AsO4) has been solved from single-crystal data. The structure is formed by layers of edge-sharing dimeric octahedra, and interconnected by chains of alternating FeO6 octahedra and AsO4 tetrahedra.