The potential of the are discharge technique for the growth of complex nanocrystallien systems is demonstrated here with the formation of quaternary superconducting nanoparticles belonging to the recently discovered intermetallic boron carbide family RNi2B2C (R = Y, Lu). The nanoparticles, which were embedded in a glassy carbon matrix and had Tc – 15 K, are reported to exhibit magnetic behavior characterized by finite size effects and weak Josephson links between the particles. The formation and characterization of the nanoparticles are detailed.