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 sup
erconductor 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.
By the application of a small oscillating magnetic field parallel to the main magnetic field and perpendicular to the transport current, we were able to generate a voltage dip in the I-V curves of Nb$_3$Sn similar to the peak-effect pattern observed
in earlier resistivity measurements. The pattern was history dependent and exhibited a memory effect. In addition we observed in the I-V curves for a high shaking-field amplitude a step feature of unknown origin.
