The antiferromagnetic ordered phase in SmRu4P12 below the metal-insulator transition at T MI = 16.5 K with an unresolved transition at T∗ ～ 14 K has been studied by resonant and nonresonant x-ray diffraction in magnetic fields. In the intermediate phase, a nonresonant Thomson scattering with q = (1,0,0) is induced by applying a magnetic field, which is presumably caused by atomic displacements reflecting the charge order in the p band, as predicted theoretically [R. Shiina, J. Phys. Soc. Jpn. 82, 083713 (2013)]. Simultaneously, the antiferromagnetic moment of Sm is enhanced along the field direction, which is considered to reflect the staggered ordering of the Γ 7 −Γ 8 crystal-field states (scalar or hexadecapole order). The present results show that the orbital-dependent p-f hybridization in association with the nesting instability in the p band gives rise to the unconventional charge order similarly with PrRu4P12 and PrFe4P12.

This work was supported by Grants-in-Aid for Scientific Research (No. 21204456, No. 21102515, and No. 2430087) from JSPS and MEXT, and by a Basic Science Research Grant from the Sumitomo Foundation.