Evolution from heavy-fermion to mixed-valence behavior in the series CePt1−xIrxSi2

To study the evolution from heavy-fermion (HF) to mixed-valence (MV) behavior upon substituting Pt for Ir in the ternary intermetallic compound CePtSi2, we carried out X-ray diffraction, dc electric resistivity, Ce LIII-edge X-ray absorption spectra (XAS), dc susceptibility and specific heat measurements in the series CePt1−xIrxSi2 (x=0,0.2,0.4,0.6,0.8,1.0). The results obtained suggest that the evolution from HF to MV behavior is likely due to the enhancement of hybridization between the Ce 4f-electron wave function and sp wave function of the adjacent transition metal ion. Besides, it was found that x∼0.6 is the borderline region between HF and MV regimes.