Studies on the superlattices of ternary alloys were recently developed, but only a new experimental results by X-ray have been reported. The ternary system of iron-aluminum-silicon, which contains the industrially important ferromagnetic alloy "Seudust" and has two superlattices of the same type on the iron-aluminum and iron-silicon sides, offers various interesting problems in connection with the superlattice theory. The present work was undertaken in this ternary system to confirm by X-ray a composition-range in which the superlattice of the 3 : 1 type can exist, because no work had yet been reported concerning it. The result showed that all ferromagnetic singularities were found in this composition-range
