A new metallofullerene Sm@C(2v)(3)-C(80) was synthesized and characterized. X-Ray analysis showed that the endohedral Sm atom undergoes a hopping motion between several off-center sites, even at low temperature. In addition, a comparative electrochemical study between Sm@C(2v)(3)-C(80) and Yb@C(2v)(3)-C(80) revealed their different redox potentials, suggesting a metal-induced effect on their redox profiles.