  We predict that CeBi in the ferromagnetic state is a Weyl semimetal. Our
calculations within density functional theory show the existence of two pairs
of Weyl nodes on the momentum path $(0, 0, k_z)$ at $15$ meV} above and $100$
meV below the Fermi level. Two corresponding Fermi arcs are obtained on
surfaces of mirror-symmetric (010)-oriented slabs at $E=15$ meV and both arcs
are interrupted into three segments due to hybridization with a set of trivial
surface bands. By studying the spin texture of surface states, we find the two
Fermi arcs are strongly spin-polarized but in opposite directions, which can be
detected by spin-polarized ARPES measurements. Our theoretical study of
quasiparticle interference (QPI) for a nonmagnetic impurity at the Bi site also
reveals several features related to the Fermi arcs. Specifically, we predict
that the spin polarization of the Fermi arcs leads to a bifurcation-shaped
feature only in the spin-dependent QPI spectrum, serving as a fingerprint of
the Weyl nodes.
