In the present study, self-assembled submicrometer-sized composite structure of bismuth-antimony (BiSb) alloy and indium antimonide (InSb) were fabricated by melt-spinning (MS) technique and spark plasma sintered (SPS) process with the eutectic composition. The power factor reached 2.6 mW/mK2 at 300 K. The thermal conductivity decreased by 35% compared with the BiSb alloy. The results suggest that this MS-SPS procedure is promising for reducing the thermal conductivity with maintaining the electrical properties.