Pressure Tuning of Superconductivity of LaPt(4)Ge(12) and PrPt(4)Ge(12) Single Crystals

We carried out electrical resistivity and X-ray diffraction (XRD) studies on the filled skutterudite superconductors LaPt [Formula: see text] Ge [Formula: see text] and PrPt [Formula: see text] Ge [Formula: see text] under hydrostatic pressure. The superconducting transition temperature [Formula: see text] is linearly suppressed upon increasing pressure, though the effect of pressure on [Formula: see text] is rather weak. From the analysis of the XRD data, we obtain bulk moduli of [Formula: see text] GPa and [Formula: see text] GPa for LaPt [Formula: see text] Ge [Formula: see text] and PrPt [Formula: see text] Ge [Formula: see text] , respectively. The knowledge of the bulk modulus allows us to compare the dependence of [Formula: see text] on the unit-cell volume from our pressure study directly with that found in the substitution series La [Formula: see text] Pr [Formula: see text] Pt [Formula: see text] Ge [Formula: see text]. We find that application of hydrostatic pressure can be characterized mainly as a volume effect in LaPt [Formula: see text] Ge [Formula: see text] and PrPt [Formula: see text] Ge [Formula: see text] , while substitution of Pr for La in La [Formula: see text] Pr [Formula: see text] Pt [Formula: see text] Ge [Formula: see text] yields features going beyond a simple picture.