Title: Unusual Hall Effect Anomaly in MnSi under Pressure
Abstract: We report the observation of a highly unusual Hall current in the helical magnet MnSi in an applied pressure $P=6--12\text{ }\text{ }\mathrm{kbars}$. The Hall conductivity displays a distinctive stepwise field profile quite unlike any other Hall response observed in solids. We identify the origin of this Hall current with the effective real-space magnetic field due to chiral spin textures, which may be a precursor of the partial-order state at $P>14.6\text{ }\text{ }\mathrm{kbar}$. We discuss evidence favoring the chiral spin mechanism for the origin of the observed Hall anomaly.