Fully gapped superconductivity in Ni-pnictide superconductors BaNi2As2   and SrNi2P2
  We have performed low-temperature specific heat $C$ and thermal conductivity $\kappa$ measurements on the Ni-pnictide superconductors BaNi$_2$As$_2$ ($T_\mathrm{c}$=0.7 K and SrNi$_2$P$_2$ ($T_\mathrm{c}$=1.4 K). The temperature dependences $C(T)$ and $\kappa(T)$ of the two compounds are similar to the results of a number of s-wave superconductors. Furthermore, the concave field responses of the residual $\kappa$ for BaNi$_2$As$_2$ rules out the presence of nodes on the Fermi surfaces. We postulate that fully gapped superconductivity could be universal for Ni-pnictide superconductors. Specific heat data on Ba$_{0.6}$La$_{0.4}$Ni$_2$As$_2$ shows a mild suppression of $T_\mathrm{c}$ and $H_\mathrm{c2}$ relative to BaNi$_2$As$_2$. 
N. Kurita, F. Ronning, C. F. Miclea, Y. Tokiwa, E. D. Bauer, A.   Subedi, D. J. Singh, H. Sakai, J. D. Thompson, R. Movshovich
cond-mat.supr-con cond-mat.str-el