  Weyl semimetal (WSM), a novel state of quantum matter, hosts Weyl fermions as
emergent quasiparticles resulting from the breaking of either inversion or
time-reversal symmetry. Magnetic WSMs that arise from broken time-reversal
symmetry provide an exceptional platform to understand the interplay between
magnetic order and Weyl physics, but few WSMs have been realized. Here, we
identify CeAlSi as a new non-centrosymmetric magnetic WSM via angle-resolved
photoemission spectroscopy (ARPES) and first-principles, density-functional
theory based calculations. Our surface-sensitive vacuum ultraviolet ARPES data
confirms the presence of surface Fermi arcs as, the smoking gun evidence for
the existence of the Weyl semimetallic state in CeAlSi. We also observe bulk
Weyl cones in CeAlSi using bulk-sensitive soft-X-ray ARPES measurements. In
addition, Ce 4f at bands are found near the Fermi level, indicating that CeAlSi
is a unique platform for investigating exotic quantum phenomena resulting from
the interaction of topology, magnetism and electronic correlations.
