Heavy fermion behavior in PrRh2B2C: Excitonic mass enhancement

We report magnetic and transport properties of a new quaternary borocarbide PrRh${}_2$B${}_2$C, based on magnetisation, resistivity and specific heat studies. This compound forms in LuNi${}_2$B${}_2$C-type tetragonal structure (space group {\it I4/mmm}) and does not exhibit magnetic ordering or superconductivity down to 0.5 K. The crystal field analysis of specific heat data suggests a singlet ground state in this compound. The high value of the Sommerfeld coefficient, $\gamma$ $\approx$ 250 mJ/mole K${}^2$, together with a singlet ground state suggests that the heavy fermion behaviour in PrRh${}_2$B${}_2$C results from the interaction of the conduction electrons with the low lying crystal field excitations. No signature of magnetic ordering or superconductivity is observed in PrRh${}_2$B${}_2$C under the application of pressure up to 23 kbar.