Evolution of magnetism in Tb(CoxNi1−x)2B2C

► Evolution of the magnetism of Tb(CoxNi1−x)2B2C was investigated. ► As x varies, different magnetic modes emerge. ► Similarly, critical temperatures and magnetic moments evolve with x. ► Such variations are almost monotonic except for the x=0.4 sample. ► Discussion is given in terms of induced Fermi-momentum variation.