Low temperature specific heat of f.c.c. ytterbium hydrides

Abstract The results of low temperature specific heat measurements of ytterbium trihydrides YbH 2.25 , YbH 2.37 and YbH 2.41 are presented. Flat maxima of C p ( T ) are observed at 3.9 K. The magnetic contribution to the specific heat is analysed in terms of Kondo and crystal field effects. Analysis of the heat capacity leads to the conclusion that f.c.c. ytterbium hydrides are heavy-formion systems with an S = 1 2 Kondo model ground state.