Presence of a fluctuation related peak but absence of vortex-lattice melting in Nb3Sn in high resolution specific-heat measurements

The melting of the magnetic vortex lattice has been observed in high-Tc superconductors in many experiments by different groups and is regarded as confirmed. To date, only one group claims to have observed the vortex-lattice melting in the low-Tc superconductor Nb3Sn in specific-heat measurements. We measured the same Nb3Sn single crystal with a differential-thermal analysis method. We report on the absence of any sign of vortex-lattice melting in our data and discuss the possible reasons for this discrepancy. In addition we confirm the observation of a small peak-like anomaly near the transition to superconductivity which is likely related to thermal fluctuations.