Abstract: An onion-like graphite 2 is produced by irradiating an electron beam to an amorphous carbon 3 under an active aluminum nanoparticle 1. By further irradiating the electron beam to the onion-like graphite 2 to intercalate aluminum atoms constituting the aluminum nanoparticle 1 in a space between (001) plane and (002) plane of the onion-like graphite 2 having a layer structure, an intercalation compound 4 is produced. Or, after the aluminum nanoparticles were driven and disposed on the onion-like graphite by electron beam, or the like, by irradiating the electron beam to intercalate aluminum atoms in the space between the (001) plane and the (002) plane of the onion-like graphite having a layer structure, the intercalation compound is produced.