Evolution of ground state properties of YbCu 5- xAu x

A substitution of Cu by Au in cubic YbCu₅ yields YbCu₄Au crystallizing in the fully ordered ternary MgCu₄Sn structure, isostructural to YbCu₅. The exchange of Cu by Au drives the system from a high T_K to a low T_K Kondo scenario, enabling long-range magnetic order to occur. Thereby, a critical concentration range is passed with the possibility of non-Fermi-liquid behavior.