Dualism of the 4 f electrons and its relation to high-temperature antiferromagnetism in the heavy-fermion compound YbCoC2

Abstract

We report on the study of the noncentrosymmetric ternary carbide YbCoC2. Our magnetization, specific heat, resistivity, and neutron diffraction measurements consistently show that the system behaves as a heavy-fermion compound, displaying an amplitude-modulated magnetic structure below the Néel temperature reaching TN = 33 K under pressure. Such a large value, being the highest among the Yb-based systems, is explained in the light of our ab initio calculations, which show that the 4 f electronic states of Yb have a dual nature, i.e., due to their strong hybridization with the 3d states of Co, 4 f states expose both localized and itinerant properties.