Structural properties of a holmium iron carbide interstitial compound, Ho2Fe17C3-x

X-raydiffractometricstudieswereperformedonasingle-crystallinespecimenoftheHo2Fe17Csx intermetallic alloy. Its crystal data (for x > 2) are a = 8.521 (2), c = 8.309 (2) A, V = 522.5 A3, hexagonalspacegroupR3lmmc. Thecrystalstructure,solvedbydirectmethods,wasrefined toafinalagreementfactorRof0.045. Theatomsaredistributedintwolayersperpendicular to the z axis: while one is composed only of iron atoms forming regular hexagonal nets, the insertion of carbons in the second layer deforms the hexagonal nets which contain holmium atoms in their center.