Structural studies by electron and x-ray diffraction of the disordered phases II' (Sn(1-x)Tb((x))Tb(4)Rh(6)Sn(18) and (Sn(1-x)Dy(x))Dy(4)Os(6)Sn(18).

(Sn(1-x)Tb(x))Tb(4)Rh(6)Sn(18) and (Sn(1-x)Dy(x))Dy(4)Os(6)Sn (18) belong to a large stannide series where there exist two chemical formulae : SnM(3)M'(4)Sn(12)(phase l and l") and SnM (4)M'(6)Sn(18) (phase ll and ll"), and four structures : l, l', ll, and ll'. That of phase ll' appeared to be cubic (a = 13.7angstroms and Fm3m space group) while the structure of phase ll is tetragonal (a = 13.7angstroms, c = 27.4angstroms and 14(1)/acd space group). Phase s/angstroms a/a ll' of the (M = Tb, M' = Rh) stannide was found to be disordered microtwinned phase ll. The disorder concerned the Tb(2) and Sn(2) sublattices of the formula : (Sn(1)(1-x)Tb(x))Tb(2)Rh (6)Sn(2)(4) Sn(3) (12)Sn(4)(2).