The invention concerns a crystalline solid, designated ITQ-31, which has the X ray diffraction diagram given below. Said solid has a chemical composition, expressed as the anhydrous base in terms of moles of oxide, defined by the general formula XO₂: mYO₂:pZ₂O₃:qR:sF, in which R represents an organic nitrogen-containing template, X represents one or more tetravalent elements other than germanium, Y represents germanium, Z represents at least one trivalent element and F is fluorine.