Crossover between Fermi liquid and non-Fermi liquid behavior in the non-centrosymmetric compound Yb$_2$Ni$_{12}$P$_7$

A crossover from a non-Fermi liquid to a Fermi liquid phase in Yb$_2$Ni$_{12}$P$_7$ is observed by analyzing electrical resistivity $\rho(T)$, magnetic susceptibility $\chi(T)$, specific heat $C(T)$, and thermoelectric power $S(T)$ measurements. The electronic contribution to specific heat, $C_{e}(T)$, behaves as $C_{e}(T)/T \sim -\ln(T)$ for 5 K $< T <$ 15 K, which is consistent with non-Fermi liquid behavior. Below $T \sim$ 4 K, the upturn in $C_{e}(T)/T$ begins to saturate, suggesting that the system crosses over into a Fermi-liquid ground state. This is consistent with robust $\rho(T) - \rho_0 = AT^2$ behavior below $T \sim$ 4 K, with the power-law exponent becoming sub-quadratic for $T >$ 4 K. A crossover between Fermi-liquid and non-Fermi liquid behavior suggests that Yb$_2$Ni$_{12}$P$_7$ is in close proximity to a quantum critical point, in agreement with results from recent measurements of this compound under applied pressure.