Magnetic Field Suppression of Ferromagnetism in Yb$_2$Pt$_3$

We have measured the heat capacity, resistivity and magnetization of single crystals of Yb$_2$Pt$_3$ grown from Pb flux. The magnetization is anisotropic and strongly non linear with field, with an Arrott plot analysis indicating ferromagnetic order. The zero field AC susceptibility is peaked at 2.4 K, where the zero field heat capacity shows a first order paramagnetic to ferromagnetic transition. This transition is suppressed by magnetic field, disappearing at a critical point, 1.75 T and 1.3 K. The zero field resistivity shows a metallic temperature dependence, and for all fields we find $\rho(T,H) = \rho_0(H) + A(H)T^2$ at sufficiently low temperature. The coefficient, A(H), has a strong maximum for H=1.75 T. It is remarkable that the application of a magnetic field decreases T$_C$ in Yb$_2$Pt$_3$, contradicting conventional expectations.