Abstract and subjects
We report the synthesis and physical properties of single crystals of stoichiometric BaNi2As2 that crystallizes in the ThCr2Si2 structure with lattice parameters a = 4.112(4) angstrom and c = 11.54(2) angstrom. The resistivity and heat capacity show a first order phase transition at T-0 = 130 K with a thermal hysteresis of 7 K. The Hall coefficient is weakly temperature dependent from room temperature to 2 K where it has a value of -4 x 10(-10) Omega cm Oe(-1). The resistivity, ac susceptibility, and heat capacity provide evidence for bulk superconductivity at T-c = 0.7 K. The Sommerfeld coefficient at Tc is 11.6 +/- 0.9 mJ mol(-1) K-2. The upper critical field is anisotropic with initial slopes of dH(c2)(c)/ dT = -0.19 T K-1 and dH(c2)(ab)/ dT = -0.40 T K-1, as determined from the resistivity.