The Sm-containing endohedral metallofullerene (EMF) Sm@C-94 has been investigated by quantum chemical and statistical thermodynamic methods. Sm@C-1(153491)-C-94 and Sm@C-3v(153493)-C-94 which both satisfy the isolated-pentagon rule (IPR) are exposed to possess considerable thermodynamic stabilities within the fullerene-formation temperature region (500-3000 K). Sm@C-3v(153493)-C-94 has been indeed determined experimentally, and a novel structure, Sm@C-1(153491)-C-94, is reported for the first time. These two isomers are related by a single Stone-Wales transformation. Meanwhile, frontier molecular orbital, natural electron configuration, and Mayer bond order analyses were employed to uncover their electronic properties. In addition, their optical spectra were simulated to support experimental identification and characterization. (C) 2015 Elsevier B.V. All rights reserved.