SMCo5 magnets are synthesized by the facile Ca reduction of core/shell-structured Co/Sm2O3 nanoparticles, as schematically illustrated in the figure. The magnets exhibit coercivities reaching 24 kOe at 100 K and 8 kOe at room temperature. The synthesis represents an important first step towards the fabrication of SmCo-based exchange-spring nanocomposites for high-performance permanent magnet applications.