Magnetic, Thermal and Transport Properties of LaNi$_2$(Ge$_{1- x}$P$_x$)$_2$

Polycrystalline samples of LaNi$_2$(Ge$_{1-x}$P$_x$)$_2$ ($x=$ 0, 0.25, 0.50, 0.75, 1) with the tetragonal ${\rm ThCr_2Si_2}$ structure were investigated by heat capacity $C_{\rm p}$, magnetic susceptibility $\chi$, and electrical resistivity $\rho$ measurements for temperatures $1.8~{\rm K}\leq T \leq 300$~K\@. The $\rho(T)$ data for each sample reveal metallic behavior that follows the Bloch-Gr\"uniesen theory. The low-$T$ $C_{\rm p}(T)$ data for the series yielded Sommerfeld coefficients $\gamma = 6$--12~mJ/mol\,K$^2$ and Debye temperatues $\Theta_{\rm D} = 300$--480~K\@. The $\chi(T)$ data showed nearly $T$-independent paramagnetism except for LaNi$_2$Ge$_2$, where data up to 1000~K exhibit a broad peak at $\approx 300$~K\@. A possible onset of superconductivity is seen for ${\rm LaNi_2P_2}$ at 2.1~K\@. Analytic functions accurately representing the Bloch-Gr\"uniesen and Debye functions are presented that are very useful for fitting $\rho(T)$ and lattice $C_{\rm p}(T)$ data, respectively.