High-energy-resolution photoemission study of and

We studied the electronic structure of isostructural (Formula presented) and (Formula presented) using high-resolution low-temperature photoemission spectroscopy. (Formula presented) is a typical valence fluctuation material, while (Formula presented) is a low (Formula presented)(∼10 K) heavy-fermion system. The valence-band spectra show that Ni 3d derived states appear at energies closer to the Fermi level ((Formula presented)) compared to the Pt 5d derived states. The near-(Formula presented) spectra exhibit the characteristic spin-orbit splitting of 4f states (4(Formula presented) and 4(Formula presented)), with higher 4(Formula presented) intensity in (Formula presented) than in (Formula presented). Numerical simulations based on the single-impurity Anderson model show that the hybridization between the conduction band and f electrons is stronger in (Formula presented) than in (Formula presented). This is qualitatively understood in terms of proximity of Ni 3d states to the f level. The obtained spectroscopic results were discussed in comparison with transport and magnetic measurements.