Non-Fermi-Liquid Effects at Ambient Pressure in a Stoichiometric Heavy-Fermion Compound with Very Low Disorder:CeNi2Ge2

Pronounced non-Fermi-liquid (NFL) effects in thermodynamic $(C,\alpha )$ and transport $\left(\rho \right)$ properties at ambient pressure $\left(p\right)$ and zero field are reported for high-purity samples of the undoped heavy-fermion compound ${\mathrm{CeNi}}_2{\mathrm{Ge}}_2$. The origin of the NFL effects is not yet clear. Novel phase transitions are observed at both finite and ambient pressure. Under $p=1.7\mathrm{}\mathrm{GPa}$, a novel, perhaps spin-density-wave-type, phase transition occurs at $T_m=0.9\mathrm{}\mathrm{K}$. At $p=0\mathrm{}$, incipient superconductivity below $T=100\mathrm{}\mathrm{mK}$ is found in the two samples with lowest residual resistivities, ${\rho }_0<0.45\mathrm{}\mu \Omega \mathrm{cm}$.