Formation, structure, and electric property of CaB4 single crystal synthesized under high pressure

Via the combination of theoretical and experimental investigations, we have synthesized the single crystal of pure calcium tetraboride (CaB4) under the conditions of high pressure and high temperature. The Temperature (T)-Pressure (P) phase diagram of Ca-B binary system has been obtained. The recovered CaB4 after decompression of high pressure is characterized to have a ThB4-type tetragonal structure. Both the calculated band structure and the measured temperature-dependent resistivity are indicative of the intrinsic metallic property of CaB4, contrary to the hypothetical semiconducting behavior.