"Kondo effect" one of the important many-body problem of an impurity spin and conduction electrons is regarded as basic back grounds of understanding heavy fermion compounds. Various models are analyzed and solved (exactly) so far. Among them, the nature of the non-Fermi liquid (NFL) in spin S=3/2 Kondo model is unresolved, which was obtained only by the numerical calculation.

We pointed out that this NFL is related to the SO(5) symmetry of S=3/2 systems. Constructing boundary conformal field theory of S=3/2 Kondo model at SO(5) symmetric point, we showed that the numerically obtained results are indeed derived by this theory. Furthermore, we newly found that the low-temperature impurity specific heat is linear in temperatures at this NFL fixed point. This is a rare example that shows non-divergent specific heat at NFL fixed point.