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Zusammenfassung:
We present the structural, magnetic, thermodynamic and transport
properties of the two new compounds YbPt2Sn and YbPt2In. X-ray powder
diffraction shows that they crystallize in different structure types,
the hexagonal ZrPt2Al and the cubic Heusler type, respectively. Despite
quite different lattice types, both compounds present very similar
magnetic properties: a stable trivalent Yb3+, no evidence for a sizeable
Kondo interaction and very weak exchange interactions with a strength
below 1 K as deduced from specific heat C(T). Broad anomalies in C(T)
suggest short range magnetic ordering at about 250 mK and 180 mK for
YbPt2Sn and YbPt2Sn, 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
YbPt2Sn evidences for a charge density wave transition at about 290 K.
The occurrence of such transitions within several RET2X compound series
(RE = rare earth, T = noble metal, X = In, Sn) is analyzed.
