[Fe3(PO4)3F2, (CH3NH3)2, H2O] or ULM-4 is a new iron phosphate with an open framework synthesized by a hydrothermal method (72 h at 453 K). The structure was solved by X-ray diffraction on single crystal. ULM-4 crystallizes in the monoclinic system (space groupP21/n(no. 14)) with cell parameters at 293 K:a=8.8494(1),b=10.3728(1),c=16.9471(1) Å,β=92.869°(1),V=1553.68 (2) Å3,Z=4. Its structure was refined toR1(F0)=0.0276, wR2(F20)=0.0741 (5033 independent reflections withI>2σ(I)). This compound is isostructural with the oxyfluorinated gallophosphate ULM-4. Its three-dimensional framework is built up from corner-sharing hexameric units, thus delimiting 10-membered channels along [010] in which methylamine and water molecules are inserted. It also exhibits 8-membered channels along [100]. A phase transition occurs at 265 K. This new compound exhibits an antiferromagnetic behavior below 25(1) K. Mössbauer spectrometry confirms the crystallographic results. © 1997 Academic Press.