  Weyl semimetals are crystalline solids that host emergent relativistic Weyl
fermions and have characteristic surface Fermi-arcs in their electronic
structure. Weyl semimetals with broken time reversal symmetry are difficult to
identify unambiguously. In this work, using angle-resolved photoemission
spectroscopy, we visualized the electronic structure of the ferromagnetic
crystal Co3Sn2S2 and discovered its characteristic surface Fermi-arcs and
linear bulk band dispersions across the Weyl points. These results establish
Co3Sn2S2 as a magnetic Weyl semimetal that may serve as a platform for
realizing phenomena such as chiral magnetic effects, unusually large anomalous
Hall effect and quantum anomalous Hall effect.
