Magnetism and Crystal Field Effect in Pr-Compounds.

Pr-based compounds exhibit a variety of ground states due to the critical role of crystalline-electric-field (CEF) effects and quadrupolar fluctuations; fascinating physics is observed when the CEF splitting energy is very low and comparable to other interactions, the unconventional heavy fermion superconductivity observed in PrOs4Sb12 is one such example. In this presentation magnetic and transport properties of few novel Pr-based compounds will be discussed and the role of crystal field effect will be examined. It will be shown that how low-lying crystal field excitations lead to excitonic mass enhancement in PrRh2B2C and Pr2Rh3Ge5. This mechanism to the heavy fermion behaviour in Pr-compounds is quite different from the usual Kondo route to heavy fermions in Ce-compounds.