In this work, through the technology of producing endohedral metallofullerene in macroscopic quanti-ties, the process of pressure polymerization of Sc2C2@C-82 and their mechanical properties have been investigated in detail using a set of experimental and theoretical methods. The crucial role of endohedral atoms is demonstrated by comparison with pristine fullerenes. It is shown that the embedding of Sc2C2 complex inside a fullerene significantly facilitates the polymerization process which finally leads to the highly rigid material at high pressures. (C) 2021 Elsevier Ltd. All rights reserved.