“…All authors agree in observing the almost perfect phase purity on the chemical composition 1:9:4 and an ordered crystal structure for this phase. Regarding the distortion on going from the cubic model to the tetragonal one, it can be roughly measured by the deviation of the lattice parameters ratio from the ideal value c/a ¼ O2 ¼ [35], CeFe 9 Si 4 [42], MCo 9 Si 4 (M ¼ La [43], Pr [41], Nd [41], Sm [44], Tb [45]), CeCo 9 Ge 4 [46], LaNi 9 Si 4 and CeNi 9 Si 4 [37], SrCu 9 Si 4 , BaCu 9 Si 4 , SrCu 9 Ge 4 and BaCu 9 Ge 4 [47], MCu 9 Sn 4 (M ¼ Nd [17], Eu [12], Yb [5], Ca [9]). …”