Successful isolation and unambiguous crystallographic assignment of a series of higher carbide cluster metallofullerenes present new insights into the molecular structures and cluster-cage interactions of endohedral metallofullerenes. These new species are identified as La2C2@C-2(41)-C-90, La2C2@D-3(85)-C-92, La2C2@C-1(132)-C-94, La2C2@C-2(157)-C-96, and La2C2@C-1(175)-C-98. This is the first report for these new cage structures except for D-3(85)-C-92. Our experimental and theoretical results deinonstrate that La2C92-106 are more inclined to exist stably in the carbide form La2C2@C90-104 rather than as the dimetallofullerenes La-2@C92-106, which are rationalized by considering a synergistic effect of inserting a C-2 unit into the cage, which ensures strong metal-cage interactions by partially neutralizing the charges from the metal ions and by fulfilling the coordination requirement of the La3+ ions as much as possible.