Comparison between Ce and Yb heavy fermion compounds: CeRh2Si2CeRh2Si2 versus YbRh2Si2YbRh2Si2

The similarities and differences of the pressure and magnetic field phase diagrams of the heavy fermion systems CeRh2Si2CeRh2Si2 and YbRh2Si2YbRh2Si2 are reviewed. In CeRh2Si2CeRh2Si2 the transition from antiferromagnetic order to a paramagnetic state seems to be first order with a clear volume discontinuity. Drastic differences appear not only in the pressure dependence of their Néel temperature but also in their magnetic field response as a comparison of the CeRu2Si2CeRu2Si2 case with YbRh2Si2YbRh2Si2 shows which reflects the position of their quantum critical field with respect to the magnetic field Kondo scale. However, a new generation of experiments in extreme conditions is required: very high magnetic field for CeRh2Si2CeRh2Si2, very low temperature for YbRh2Si2YbRh2Si2.