  We study a two-dimensional phase of chromium bismuthate (CrBi), previously
unknown material with exceptional magnetic and magnetooptical characteristics.
Monolayer CrBi is a ferromagnetic metal with strong spin-orbit coupling induced
by the heavy bismuth atoms, resulting in a strongly anisotropic Ising-type
magnetic ordering with the Curie temperature estimated to be higher than 300 K.
The electronic structure of the system is topologically nontrivial, giving rise
to a nonzero Berry curvature in the ground magnetic state, leading to the
anomalous Hall effect with the conductivity plateau of $\sim$1.5 $e^2/h$ at the
Fermi level. Besides, monolayer CrBi demonstrates the magnetooptical Kerr
effect in the visible and near-ultraviolet spectral ranges with the maximum
rotation angles of up to 10 mrad. Remarkably, the magnetooptical response is
strongly dependent on the direction of magnetization, which makes monolayer
CrBi a promising system for practical applications in magnetooptical and
spintronic devices.
