  Topological quantum phases have been largely understood in weakly correlated
systems, which have identified various quantum phenomena such as spin Hall
effect, protected transport of helical fermions, and topological
superconductivity. Robust ferromagnetic order in correlated topological
materials particularly attracts attention, as it can provide a versatile
platform for novel quantum devices. Here, we report singular Hall response
arising from a unique band structure of flat topological nodal lines in
combination with electron correlation in an itinerant, van der Waals
ferromagnetic semimetal, Fe3GaTe2, with a high Curie temperature of Tc=360 K.
High anomalous Hall conductivity violating the conventional scaling,
resistivity upturn at low temperature, and a large Sommerfeld coefficient are
observed in Fe3GaTe2, which implies heavy fermion features in this
ferromagnetic topological material. Our circular dichroism in angle-resolved
photoemission spectroscopy and theoretical calculations support the original
electronic features in the material. Thus, low-dimensional Fe3GaTe2 with
electronic correlation, topology, and room-temperature ferromagnetic order
appears to be a promising candidate for robust quantum devices.
