  A recent paper of Chen et al. claims to have derived an allegedly previously
unavailable "unified" Andreev Reflection (AR) formalism for an arbitrary spin
polarization P that recovers earlier results as its special limits. In this
Comment we show that, contrary to this claim, there are numerous works
correctly solving the problem formulated in this paper for an arbitrary P,
while Chen et al formulas fail to correctly incorporate P \neq 0 effects and
violate basic physical principles.
