All the known phases in the PbF2/SnF2 system have structures derived from the fluorite-type β-PbF2, and are either disordered, and therefore cubic, or ordered with lattice distortion and superstructures. In addition, they are the highest performance fluoride-ion conductors, with PbSnF4 being the very best. In this work, a new phase, Pb2SnF6 has been prepared and characterized. Contrary to the other lead(II) tin(II) fluorides known up to date, the structure of Pb2SnF6 is a superstructure of a-PbF2, instead of β-PbF2, with a large (4 × 4) bidimensional supercell. Pb2SnF6 is prepared by the reaction of a-PbF2 with an aqueous solution of SnF2.