Suppression of p-f mixing and formation of a superzone gap in CeSbNi_x

We report electrical resistivity, Hall coefficient, magnetic susceptibility, magnetization, and magnetoresistance measurements on CeSbNi_x (0 ≤x ≤0.4), where the Ni atoms are incorporated interstitially into the cubic cell of CeSb. The Néel temperature T_N drops from 16 K for x=0 to 9 K for x=0.05 and then gradually increases to 12.5 K for x=0.4. The initial depression of both T_N and saturation moment is ascribed to the collapse of p-f mixing by the decrease of the 5p-hole concentration in the semimetallic CeSb. The resistivity for x≥0.08 shows a sharp rise just below T_N, which is quenched by the application of magnetic fields higher than the metamagnetic transition field. This finding indicates that a superzone gap is formed in the 5d-electron band of CeSbNi_x for x≥0.08 as a result of the type-I antiferromagnetic order.