Superconducting properties of BeB2.75
We present the low-temperature electronic transport properties of the intermetallic commonly known as BeB2. In contrast to the much simpler A1B2-type structure of the 39-K superconductor MgB2, BeB2 forms a complex structure-type that is nearly unique in nature. The structure has 110.5 atoms per unit cell and a stoichiometry BeB2.75. Polycrystalline Be(10.8B)2.75 is superconducting below Tc=0.72 K with a critical magnetic field Hc2=0.175 T. Isotopically pure 10.0B samples have an enhanced Tc=0.79 K. Hall-effect measurements suggest that the material is intrinsically compensated.