Isotropic Field Driven Insulator-to-Metal transition in GdPS.*

We synthesized single crystals for GdPS and studied its electronic properties. GdPS crystalizes in an orthorhombically distorted ZrSiS-type structure. Unlike ZrSiS which possess topological semimetal phase with excellent metallicity, GdPS exhibit non-metallic transport that is consistent with the existence of a bulk band gap found in electronic band calculations. Furthermore, in contrast to the extremely large positive magnetoresistance in ZrSiS, GdPS display a colossal negative magnetoresistance reaching nearly 100% (normalized to zero field resistivity) at 2 K, which effectively leads to a field driven insulator-to-metal transition. Furthermore, such colossal negative magnetoresistance is insensitive to the orientation of the applied magnetic field, which is distinct from most of the previously established negative magnetoresistance material systems. Through combined experimental and theoretical investigation, we found that such unusual behavior is caused by the isotropic d-f magnetic exchange splitting for Gd, which drives an insulator-to-metal transition that is isotropic with respect to magnetic field. Our findings may establish a new direction towards antiferromagnetic materials with isotropic magneto transport properties which creates a rare platform for spintronics.