Quantum critical phenomena in undoped heavy-fermion metals

We present results of low-temperature calorimetric and resistive measurements on the isostructural heavy-fermion compounds CeCu2Si2 and CeNi2Ge2. 'Non-Fermi-liquid' effects are established which suggest the nearness of an antiferromagnetic quantum critical point (QCP) in both systems. The observed deviations from the properties of a Landau Fermi liquid (FL) may be related to anomalous energy dependences of both the quasiparticle mass and the quasiparticle-quasiparticle scattering cross section. For CeNi2Ge2, a moderately heavy FL can be recovered by application of moderate values of either magnetic field or hydrostatic pressure. For p = 1.7 GPa a novel, non-superconducting, phase transition has been discovered at T-1 similar or equal to 1 K.