Highly concentrated slurry preparation and low-temperature pressureless sintering of SiC using a novel Al3BC3 additive were investigated. Al+B4C+C powder mixture, which is a conventional sintering additive system of SiC, could not be dispersed in ethyl alcohol above 10 vol%. In contrast, Al3BC3 slurry (average particle size: 0.5 mu m) could be prepared up to 50 vol% solid loading and SiC slurry containing 10 wt% Al3BC3 was successfully fabricated up to 45 vol%. The relative density of SiC was 97.9% after pressureless sintering at 1850 degrees C. Young's modulus and hardness of a sintered SiC were 411 and 22.5 GPa, respectively. The present report proposes a method for the low-temperature pressureless sintering of SiC specimens having complex shape and fair mechanical properties by the application of a ternary compound (Al3BC3) as a novel-sintering additive.