  Nature of the field-induced charge ordered phase (phase II) of
SmRu$_4$P$_{12}$ has been investigated by resonant x-ray diffraction (RXD) and
polarized neutron diffraction (PND), focusing on the relationship between the
atomic displacements and the antiferromagnetic (AFM) moments of Sm. From the
analysis of the interference between the non-resonant Thomson scattering and
the resonant magnetic scattering, combined with the spectral function obtained
from x-ray magnetic circular dichroism, it is shown that the AFM moment of Sm
prefers to be parallel to the field ($m_{\text{AF}} \parallel H$), giving rise
to large and small moment sites around which the P$_{12}$ and Ru cage contract
and expand, respectively. This is associated with the formation of the
staggered ordering of the $\Gamma_7$-like and $\Gamma_8$-like crystal-field
states, providing a strong piece of evidence for the charge order. PND was also
performed to obtain complementary and unambiguous conclusion. In addition,
isotropic and continuous nature of the phase II is demonstrated by the
field-direction invariance of the interference spectrum in RXD. Crucial role of
the $p$-$f$ hybridization is shown by resonant soft x-ray diffraction at the P
$K$-edge ($1s\leftrightarrow 3p$), where we detected a resonance due to the
spin polarized $3p$ orbitals reflecting the AFM order of Sm.
