A set of compounds with the general formula M8C12, where M is a transition element such as titanium, vanadium, or iron. These compounds were formerly known as metallo-carbohedrenes. The structure of a metallocarbohedryne is a distorted cube, with the eight metal atoms at the vertices and the twelve carbon atoms arranged diagonally in pairs across each of the faces. An equivalent description of this structure is that it consists of two intersecting concentric tetrahedra with opposite orientations, with the metal atoms at the vertices and the carbon atoms arranged in pairs on the edges of one of the tetrahedra. Metallocarbohedrynes can be prepared by vaporizing the metal with a laser in an atmosphere consisting of a suitable hydrocarbon.