SEMICONDUCTING BEHAVIOR OF THE INTERMETALLIC COMPOUND AL2RU

We present data on transport properties of polycrystalline samples of the intermetallic compound Al2Ru. The high d.c. conductivity ratio sig ma(300 K)/sigma(0.46 K) approximate to 50. and low conductivity sigma( 0.46 K)=0.21 Omega(-1) cm(-1) are anomalous for metal-based alloys. At high temperature, above 500 K, sigma exhibits an activated behavior i ndicative of an energy gap in reasonable agreement with band structure calculations and optical-conductivity results. Analysis of results on a large number of samples suggests also the existence of a small intr insic band inside the gap, Transport and magnetotransport experiments indicate that Al2Ru is a classical semiconductor even at low temperatu re.