Pressure-Induced Interplay between Heavy-Fermion and Mn-Derived Magnetic States in CeMnSi

We investigated pressure effects on the nontrivial heavy-fermion antiferromagnet CeMnSi by means of electrical resistivity (ρ) and powder X-ray diffraction. With increasing pressure, the antiferromagnetic order of Mn (T N ∼ 240 K at ambient pressure) is rapidly suppressed and disappears at P c ∼ 1.3 GPa. Instead, a pressure-induced anomaly appears at T M ∼ 97 K and shifts to higher temperatures with increasing pressure. This anomaly suggests a pressure-induced modification of the Mn-derived magnetic state, accompanied by a significant change in the Ce-4f electronic state. In the low-pressure region, non-Fermi-liquid-like behavior characterized by nearly T-linear resistivity is observed around 0.7 GPa. In addition, ρ shows a marked reduction below T M and a qualitative change toward more metallic behavior above the structural transition pressure P s ∼ 5.7 GPa. At ambient pressure, CeMnSi exhibits negative thermal expansion below ∼40 K, which is absent in LaMnSi, supporting the formation of a heavy-fermion ground state.