  Quadratic band crossing points (QBCPs) and quantum anomalous Hall effect
(QAHE) have attracted the attention of both theoretical and experimental
researchers in recent years. Based on first-principle calculations, we find
that the FeB$_2$ monolayer is a nonmagnetic semimetal with QBCPs at $K$.
Through symmetry analysis and $\mathbf{k}\cdot\mathbf{p}$ invariant theory, we
find that the QBCP is not protected by rotation symmetry and consists of two
Dirac points with same chirality (Berry phase of $2\pi$). Once introducing
Coulomb interactions, we find that there is a
spontaneous-time-reversal-breaking instability of the spinful QBCPs, which
gives rise to a $C=2$ QAH insulator with orbital moment ordering.
