Field induced phases in the antiferromagnet UPt₂Si₂

Previously, UPt₂Si₂ has been described as a moderately mass enhanced antiferromagnet with a transition temperature of T_N = 32K [1]. In contrast, and more recently, it has been demonstrated that UPt₂Si₂ closely resembles the tetragonal heavy fermion superconductor/hidden order material URu₂Si₂ in various physical properties [2,3]. We present a detailed study of high field magnetization and resistivity on single crystalline UPt₂Si₂. While up to now the high field behavior of UPt₂Si₂ was discussed in terms of a crystalline electric field scheme applied to an f electron local moment system [4], we show that the high field behavior is much more complex than previously thought. In particular, the magnetic phase diagrams derived from our measurements contain various field induced phases, again analougous to URu₂Si₂. We compare the phase diagrams of both systems and discuss possible scenarios accounting for such behavior in UPt₂Si₂.