A simple process for depositing a coating of silicon carbide (SiC) crystallites similar to10 mn in size onto diamond particles has been developed. SiO powders react with diamond in a vacuum at 1350degreesC to form a uniform beta-SiC polycrystalline layer similar to60 nm thick. The SiC coating improves the oxidation resistance of the diamond. A cemented carbide material containing 20-vol%-SiC-coated diamond particles was sintered to a relative density of 99.5% by pulsed-electric-current sintering. A Vickers hardness and indentation fracture toughness of 15 GPa and 16.3 MPa(.)m(1/2), respectively, were obtained. This toughness is two times higher than that of cemented carbide containing no particles. The higher toughness is attributed to deflection and blockage of crack propagation by the diamond particles.