We develop a phenomenological theory for the family of uranium-based heavy fermion superconductors ($URhGe$, $UCoGe$, and $UTe_2$ ). The theory unifies the understanding of both superconductivity(SC) with a weak magnetic field and reentrant superconductivity(RSC) that appears at the first-order transition line with a high magnetic field. It is shown that the magnetizations along the easy and hard axis have opposite effects on superconductivity. The RSC is induced by the fluctuation parallel to the direction of the magnetic field. The theory makes specific predictions about the variation of triplet superconductivity order parameters $vec{d}$ with applied external magnetic fields and the existence of a metastable state for the appearance of the RSC.
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