Continuing our search on semiconducting compounds and alloys, the InAs 50 mol%-CuInSe2 50 mol% alloy was investigated. Both InAs and CuInSe are adamantine which satisfies the four electron per atom rule. A large single crystal ingot was carefully prepared using the vertical Bridgmans method. The specimen was examined by room temperature and temperature dependence X-ray powder photography, Electron Probe Microanalysis (EPMA), Differential Thermal Analysis (DTA), and Vickers hardness test.