Synthesis, single crystal X-ray diffraction, Mössbauer and magnetic studies of a new iron phosphate Rb₉Fe₇(PO₄)₁₀ are described. This compound crystallizes in the monoclinic system with the space group P2₁/<i>a</i> and the following parameters: <i>a</i> = 9.886(4) Å, <i>b</i> = 16.493(2) Å, <i>c</i> = 13.437(2) Å, <i>β</i> = 110.49(3)° and <i>Z</i> = 2. Its structure is closely related to that of the Cs_9−<i>x</i>K_<i>x</i>Fe₇(PO₄)₁₀ phosphates. The 3D framework consists of FeO₆ and FeO₅ polyhedra and Fe₂O₁₀ units of corner-sharing FeO₆ and FeO₅ polyhedra. These units are linked to each other by the phosphate tetrahedra in such a way that the resulting framework forms large intersecting tunnels extending along the <i>a</i> and <i>c</i> directions, where the Rb⁺ cations are located. A high temperature X-ray powder diffraction study showed a partial decomposition of the product above 773 K. The magnetic susceptibility results are consistent with Fe(III) showing an antiferromagnetic ordering below <i>T</i>_N ≈ 19 K and a paramagnetic behavior in the range of 50–300 K. The application of the Curie–Weiss law yields an effective moment of 5.99 μ_B in a good agreement with the ideal spin only value of 5.92 μ_B for d⁵-iron(III). The distribution of iron and its local environments were confirmed by a Mössbauer study undertaken at 293 and 4.2 K.< Réduire