The effect of transmutation of a metallic element encaged in C-82 through EC radioactive decay was studied for the Gd-146 --> (EU)-E-146 --> Sm-146 decay series. The metallofullerene containing the EC decay progeny (EU)-E-146 was found chemically stable and eluted in a HPLC separation at a retention time which corresponded to the retention time of one of the minor isomers of Eu @ C-82(3). As the oxidation state of the metal atom in Gd @ C-82 and Eu @ C-82 is known to be +3 and +2, this result suggests that the C-82 cage which forms a chemically stable metallofullerene with the metal atom at the +3 oxidation state can also form a stable metallofullerene with a metal atom at the +2 oxidation state.