Heavy-electron antiferromagnetism inCePt2Sn2

We have measured specific heat, magnetic susceptibility, and resistivity on the cerium-intermetallic compound ${\mathrm{CePt}}_2$ ${\mathrm{Sn}}_2$. The heat capacity shows a strong increase below a few kelvin, typical of a large many-body enhancement of the density of states or equivalently of the effective electronic mass. Just before the material orders antiferromagnetically at ${\mathit{T}}_{\mathit{N}}$=0.88 K, the linear temperature coefficient of the specific heat γ is approximately 3.5 J/mol ${\mathrm{K}}^2$, making this material one of the heaviest electron systems known. The low Néel temperature and huge specific heat imply similarly low-energy scales for competing RKKY and Kondo-like interactions.