Dualism Of The 4f Electrons And Its Relation To High-Temperature Antiferromagnetism In The Heavy-Fermion Compound Ybcoc2

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 Neel temperature reaching T-N = 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 4f electronic states of Yb have a dual nature, i.e., due to their strong hybridization with the 3d states of Co, 4f states expose both localized and itinerant properties.