Semi-classical origin of the extreme magnetoresistance in PtSn4

The so-called “extreme magnetoresistance” (XMR) found in few conductors poses interesting conceptual challenges which address needs in technology. In contrast to the more common XMR in semi-metals, PtSn 4 stands out as a rare example of a high carrier density multi-band metal exhibiting XMR, sparking an active debate about its microscopic origin. Here we report a sharp sensitivity of its XMR upon the field angle, with an almost complete collapse only for one specific current and field direction (B// b , I// a ). Corroborated by band-structure calculations, we identify a singular open orbit on one of its Fermi surface sheets as the origin of this collapse. This remarkably switchable XMR resolves the puzzle in PtSn 4 as a semi-classical effect of an ultra-pure, compensated carrier metal. It further showcases the importance of Ockham’s razor in uncommon magnetotransport phenomena and demonstrates the remarkable physical properties conventional metals can exhibit given they are superbly clean. Extreme magnetoresistance (XMR) is the name assigned to the large and non-saturating magnetoresistance that occurs in some metals and semi-metals. In this work, the authors demonstrate the first material, PtSn 4 , in which XMR can be switched off by changing the direction of the magnetic field.