A theoretical formalism of Andreev reflection is proposed to provide a theoretical support for distinguishing the singlet pairing and the triplet pairing by the point contact Andreev reflection (PCAR) experiments, in contrast to the previous models designed only for the singlet pairing case. We utilize our theoretical curves to fit the data of the PCAR experiment on the unconventional superconductivity in the $Bi/Ni$ bilayer [arXiv:1810.10403], and find the Anderson-Brinkman-Morel state satisfies the main characteristics of the experimental data. Moreover, the Andreev reflection spectra of the Balian-Werthamer state and the chiral $p$-wave are also presented.
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