in high magnetic fields*

Magnetoresistance measurements with the current in the basal plane were performed on single crystals of URu_2-xFe_xSi₂ as a function of magnetic field H, angle θ of H with respect to the c-axis, and temperature T for several Fe concentrations x in the “hidden order” (HO) and large moment antiferromagnetic (LMAFM) regions of the T vs. x phase diagram. Measurements were made in DC fields of up to 33 T and pulsed fields of up to 65 T at the National High Magnetic Field Laboratories at Tallahassee and at Los Alamos, respectively. The Fourier components of the angular-dependence of the magnetoresistance for rotation about an axis through the basal plane were mapped out as a function of H, θ, T, and x through the HO and LMAFM phase transitions and the dependences of the HO and LMAFM transition temperatures on θ, H, and x were determined.