  We present the structural, magnetic, thermodynamic, and transport properties
of the two new compounds YbPt$_2$Sn and YbPt$_2$In. X-ray powder diffraction
shows that they crystallize in different structure types, the hexagonal
ZrPt$_2$Al and the cubic Heusler type, respectively. Despite quite different
lattice types, both compounds present very similar magnetic properties: a
stable trivalent Yb$^{3+}$, no evidence for a sizeable Kondo interaction, and
very weak exchange interactions with a strength below 1K as deduced from
specific heat $C(T)$. Broad anomalies in $C(T)$ suggest short range magnetic
ordering at about 250mK and 180mK for YbPt$_2$Sn and YbPt$_2$In, respectively.
The weak exchange and the low ordering temperature result in a large
magnetocaloric effect as deduced from the magnetic field dependence of $C(T)$,
making these compounds interesting candidates for magnetic cooling. In addition
we found in YbPt$_2$In evidences for a charge density wave transition at about
290K. The occurrence of such transitions within several RET$_2$X compound
series (RE = rare earth, T = noble metal, X = In, Sn) is analyzed.
