Metamagnetism and the Fifth Order Susceptibility in UPt3
  An enhanced susceptibility is a natural consequence of the "heavy fermion" (HF) state rendering the possibility of measurably large nonlinear susceptibilities. In recent work a universal behavior of the peaks observed in the linear (\Chi_1) and the third order (\Chi_3) susceptibility in HF metamagnets has been identified. This universality is well accounted for by a single energy scale model considering on-site correlations only. A prediction of this model is a peak in the fifth order susceptibility, \Chi_5, as well. In the first measurements on a HF metamagnet, UPt3 reported herein, we find that Chi_5 rather than attaining a peak, saturates at low temperatures and is positive. The thermodynamic implications of these towards the stability of the metamagnetic HF state are discussed. 
B.S.Shivaram, Brian Dorsey, D.G. Hinks and Pradeep Kumar
cond-mat.str-el