Evidence for Bulk Superconductivity in $K_3{C}_{60}$ Single Crystals

A detailed study of the supercurrent flow in ${\mathrm{K}}_3{\mathrm{C}}_{60}$ single crystals is presented. From dc magnetization and ac susceptibility measurements we obtain the sample dimension over which the superconducting currents flow. We find that this dimension is identical to the sample size and, therefore, demonstrates the bulk nature of superconductivity in fullerenes in an unambiguous way.