Semicarbides in a new high-temperature (1600C) ordered state were observed for the first time, and were characterized by means of X-ray diffraction. This revealed the presence of an ordered distribution of some 5 to 6% of structural vacancies over every second sheet of the metal-atom close packing, and a statistical distribution of C atoms over the octahedral interstices.

Ordered Modifications of Niobium and Molybdenum Semicarbides with Long-Range Order in Distribution of Structural Metal Vacancies. B.V.Khaenko, O.A.Gnitetskii, M.V.Karpets: Kristallografiya, 1999, 44[2], 317-20 (Crystallography Reports, 1999, 44[2], 281-4)