Transition from dense Kondo to the intermediate-valence regime in the Ce(Pt1-xNix)2Si2 alloys

Electrical resistivity p(T) measurements on polycrystalline samples of the Ce(Pt1-xNix)(2)Si-2 system exhibit dense Kondo behaviour for alloys with 0 less than or equal to x less than or equal to 0.6. The temperature at which a maximum appears in p(T) shifts from T-max = 65 K for x = 0 to T-max = 290 K for x = 0.6 as the system evolves towards the intermediate-valence regime for the CeNi2Si2 compound. At low temperatures the Ce(Pt1-xNix)(2)Si-2 alloys show a Fermi liquid T-2 contribution to p (T) below the coherence temperature T-coh. It is observed that T-coh approximate to T-K/(2(j + 1)), with a transition that takes place from a dense Kondo regime of T-K < T-CF (j = 1/2, E-R approximate to E-F) to a regime of T-K > T-CF (j = 5/2, E-R > E-F) TK (alphaT(max)) and T-CF denote the Kondo and crystalline electric field splitting, EF and ER are the Fermi and the Abrikosov-Suhl resonance energies and j denotes the total angular momentum. An electronic Gruneisen parameter value Omega = - partial derivative (In T-max)/partial derivative (In V) of 19 has been obtained for the alloy system which is in reasonable agreement with Q = 28 found from pressure studies on CePt2Si2 It is argued that volume effects are mainly responsible for the hybridization in the Ce(Pt1-xNix)(2)Si-2 system and application of the compressible Kondo lattice model to T-max data yields \ J N(E-F) \ = 0.309 +/- 0.008, where J is the on-site exchange interaction between conduction electrons and the localized 4f spin and N(E-F) is the density of states at E-F.