  We investigate interference of Majorana fermions (MFs) in NS junctions. A
general formula of charge conductance G for NS junctions with two MFs is
derived based on the low energy effective model. It is found that G for two MFs
takes various values 0 \leq G \leq 4e^2/h owing to interference of the MFs,
while G is quantized as G = 2e^2/h for a single MF. The value of G is
determined by symmetry of the system. As an example, we investigate the
complete destructive interference of two degenerate MFs reported by Ii et al.
[A. Ii, A. Yamakage, K. Yada, M. Sato, and Y. Tanaka, Phys. Rev. B 86, 174512
(2012)], and identify the symmetry responsible for the destructive
interference.
