  In bilayer quantum Hall (BLQH) systems at $\nu$=2, three different kinds of
ground states are expected to be realized, i.e. a spin polarized phase (spin
phase), a pseudospin polarized phase (ppin phase) and a canted
antiferromagnetic phase (C-phase). An SU(4) scheme gives a powerful tool to
investigate BLQH systems which have not only the spin SU(2) but also the layer
(pseudospin) SU(2) degrees of freedom. In this paper, we discuss an origin of
the C-phase in the SU(4) context and investigate SU(4) coherent effects to it.
  We show peculiar operators in the SU(4) group which do not exist in
SU$_{\text{spin}}$(2)$\otimes$SU$_{\text{ppin}}$(2) group play a key role to
its realization. It is also pointed out that not only spins but also
pseudospins are ``canted'' in the C-phase.
