Comment on "Unified Formalism of Andreev Reflection at a Ferromagnet/Superconductor Interface" by T.Y. Chen, et al

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.