H-T phase diagram of the metamagnetic transition in $URu_2Si_2$,   measured in high d. c. magnetic fields
  We have studied the ultrasonic velocity and ac susceptibility of $URu_2Si_2$ in d. c. magnetic fields up to 45T. A significant difference between the constructed H-T phase diagram and that extracted from earlier pulsed fields measurements can be explained in terms of a large magnetocaloric effect. A hysteresis of metamagnetic transition at low temperatures and a new phase separation line have been observed for the first time. 
A. Suslov, J. B. Ketterson, D. G. Hinks and Bimal K. Sarma