  The kagome-lattice crystal hosts various intriguing properties including the
frustrated magnetism, charge order, topological state, superconductivity and
correlated phenomena. To achieve high-performance kagome-lattice compounds for
electronic and spintronic applications, careful tuning of the band structure
would be desired. Here, the electronic structures of kagome-lattice crystal
Ni3In2S2 were investigated by transport measurements, angle-resolved
photoemission spectroscopy as well as ab initio calculations. The transport
measurements reveal Ni3In2S2 as a compensated semimetal with record-high
carrier mobility (~8683 cm2 V-1 S-1 and 7356 cm2 V-1 S-1 for holes and
electrons) and extreme magnetoresistance (15518% at 2 K and 13 T) among
kagome-lattice materials. These extraordinary properties are well explained by
its band structure with indirect gap, small electron/hole pockets and large
bandwidth of the 3d electrons of Ni on the kagome lattice. This work
demonstrates that the crystal field and doping serve as the key tuning knobs to
optimize the transport properties in kagome-lattice crystals. Our work provides
material basis and optimization routes for kagome-lattice semimetals as
electronics and spintronics applications.
