Sm-Co intermetallic compound nanoparticles were obtained by utilizing plasma-induced cathodic discharge electrolysis in molten chloride electrolyte under a 1 atm Ar atmosphere. To form intermetallic nanoparticle, an electrochemical implantation method was adopted. Before conducting electrochemical implantation, we investigated the electrolytic condition to form Co nanoparticle to be used as a precursor. The size and crystal structure of the obtained Co nanoparticle strongly depended on the melt temperature. Hexagonal petaline epsilon-Co nanoparticles were obtained below 400 degrees C, and spherical alpha-Co nanoparticles were obtained above 400 degrees C. The size of the obtained spherical alpha-Co particle increased from 112 to 230 nm with increasing melt temperature. Using spherical alpha-Co nanoparticles, which were formed at 450 degrees C in the melt by plasma-induced cathodic discharge electrolysis and piled-up on the Mo plate as a working electrode, SmCo(2) and SmCo(3) intermetallic nanoparticles were obtained by electrochemical implantation of Sm into alpha-Co nanoparticles. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.012201jes]