Thermal expansion and magnetostriction of Yb2Fe12P7 single crystals

The noncentrosymmetric heavy-fermion compound Yb2Fe12P7 exhibits a magnetic transition at ∼1 K. Recent resistivity measurements reveal non-Fermi-liquid behavior in an extended temperature and field range. From the unusual low-temperature behavior it was concluded that Yb2Fe12P7 belongs to the growing class of compounds in which the non-Fermi-liquid behavior does not conform to the standard QCP scenario which can be described by the Hertz-Millis-Moriya theory. We report on thermal expansion and magnetostriction measurements in a temperature range of 40 mK<T<10 K and magnetic fields of up to 14 T parallel and perpendicular to the hexagonal c axis. From the data we construct (T,B) phase diagrams for both field directions. The Grueneisen ratio calculated from our measurements is comparatively small and does not diverge for T→0. It gives, therefore, no evidence for a nearby pressure-induced quantum critical point.