The discovery of a new isomer of the endohedral metallofullerene Sc3N@C-80 is reported. C-13 labeled (similar to9%) Sc3N@C-80 has been synthesized and has been characterized by HPLC, mass spectroscopy and C-13 NMR data. The C-13 NMR spectrum shows six peaks with a 1:2:2:1:1:1 ratio that are assigned to the D-5h isomer. The results of theoretical calculations are also reported for the I-h and D-5h isomers of SC3N@C-80. (C) 2003 Elsevier Science B.V. All rights reserved.