Specific heat of metastable Zr1-xSix alloys

Non-equilibrium phases in the system Zr 1-x Si x prepared by liquid quenching are superconducting with intermediate electron-phonon coupling as determined from specific heat, low-field DC magnetisation and electrical resistance measurements. Analysis of the authors data clearly shows that amorphous samples (0.12<or=x<or=0.20) are more homogeneous compared to samples of a metastable BCC phase (0.08<or=x<or=0.11). In the latter samples, a minority phase, presumably amorphous, strongly influences the superconducting properties. The concentration dependence of the transition temperature T c of the majority phase is dominated by the electronic density of states. The data at very low temperatures suggest the existence of a linear specific heat contribution which may be due to the presence of two-level tunnelling states in both places.