We report the synthesis and physical properties of single crystals of stoichiometric BaNi2As2 that crystalizes in the ThCr2Si2 structure with lattice parameters a = 4.112(4) \AA and c = 11.54(2) \AA. 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 -4x10^{-10} \Omega-cm/Oe. Resistivity, ac-susceptibility, and heat capacity find evidence for bulk superconductivity at T_c = 0.7 K. The Sommerfeld coefficient at T_c is 11.6 \pm 0.9 mJ/molK^2. The upper critical field is anisotropic with initial slopes of dH_{c2}^{c}/dT = -0.19 T/K and dH_{c2}^{ab}/dT = -0.40 T/K, as determined by resistivity.
@article{arxiv.0807.3788,
title = {First Order Phase Transition and Superconductivity in BaNi2As2 Single Crystals},
author = {F. Ronning and N. Kurita and E. D. Bauer and B. L. Scott and T. Park and T. Klimczuk and R. Movshovich and J. D. Thompson},
journal= {arXiv preprint arXiv:0807.3788},
year = {2008}
}