A systematic powder X-ray structure study for (Sc2C2)@C-82(isomer III) and (Y2C2)@CS2(III) is carried out by the MEM/Rietveld method by using high resolution synchrotron radiation powder data. In both fullerene materials, two carbon atoms are encapsulated in the cage and a M2C2 bent cluster is most likely formed in the cage. The obtained cage structure Of SC2C84(III) is C-82-C-3V(8), which is the same as those Of (Y2C2)@C-82(III) and Y-2@C-82(III). The charge density Of C-2 is located at the center of fullerene cage. Two scandium atoms show the rotational disorder, indicating the presence of a rapid hopping motion inside C-82-C-3V(8) cage. The inter-atomic distances between metal and carbon atoms on fullerene cage are 2.29 angstrom for (Sc2C2)@C-82(III), which is 0.2 A smaller than that of (Y2C2)@C-82(III). (c) 2006 Elsevier B.V. All rights reserved.