We report resistivity, nuclear quadrupole resonance (NQR), and magnetization measurements under high pressures in a novel heavy fermion compounds SmOs4Sb12. The resistivity and nuclear spin-lattice relaxation rate 1/T1 show the coherent behavior below a characteristic temperature T * = 20 − 25 K at ambient pressure. Nuclear spin-spin relaxation rate 1/T2 was found to show a peak of electrical origin around T * . Some charge fluctuation is considered to play an important role in the Kondo effect of SmOs4Sb12. On the other hand, the magnetization at low temperature does not increase under pressures, although the transition temperature increases. The NQR signals are strongly suppressed around the transition temperature and vanishes at low temperatures. These suggest that the ordered state in SmOs4Sb12 is not simple ferromagnetism.

Heat capacity and ac-susceptibility measurements under high pressure are carried out in SmOs 4 Sb 12 . Application of pressure increases the Curie temperature T C and enhances the heat-capacity jump at T C . On the other hand, the peak value of ac-susceptibility at T C decreases above 1 GPa and then almost vanishes at 3.6 GPa. These experimental facts suggest that the ordered state in SmOs 4 Sb 12 is not simple ferromagnetic state but possibly multipolar ordered state.

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