The endohedral nature of dimetallofullerene Sc{sub 2}{at}C{sub 84} is determined for the first time by a method which is a combination of the maximum entropy method (MEM) and the Rietveld refinement from synchrotron powder diffraction data. The obtained MEM charge density clearly shows the D{sub 2d}-symmetry cage structure, indicating the rotation of Sc{sub 2}{at}C{sub 84} molecules in solid state is almost quenched even at room temperature. From the MEM charge density, the encapsulated Sc-Sc distance and the nearest Sc-C distance are 3.9(1) and 2.4(1)A, respectively. {copyright} {ital 1997} {ital The American Physical Society}