## 4 Soldering and Sample Mounting  
The contact electrical resistance, and, thus, the development of heat due to ohmic heating, could have affected both measurement reliability (due to heat propagation) and efficiency (due to helium evaporation and consumption). This factor is directly related to the effectiveness of the soldering process. We evaluated different traditional low-melting-point soldering alloys, such as Bi-Sn, Pb-Sn, and In-Sn. Focusing on the last two, while Pb-Sn was characterized by higher mechanical and electrical properties, the latter exhibited a lower melting point (approx. 120 \({}^{\circ}\)C vs. 190 \({}^{\circ}\)C), which could represent a significant advantage in terms of avoiding sample degradation due to thermal factors [8]. To assess the difference in contact resistance due to two soldering alloys, we carried out resistance measurement in a liquid nitrogen bath comparing couples of superconducting tapes soldered among them with different alloys. We obtained values of the inter-tape electrical resistance close to 50 n\(\Omega\cdot\)cm\({}^{2}\) in both cases. Rather than focusing on the absolute value, which may be influenced by several factors ascribable to the nature of the tape surface due to its manufacturing [9], we observed a 20% difference in favor of the Pb-Sn alloys, which exhibited lower values. We decided that the processing ease due to the melting temperature gain was more favorable than the enhancement in the electrical properties and  
Figure 8: Field/current curves acquired at 4.2 K for a Shanghai Technologies tape on the angular sample holder with the field parallel to the tape surface at various magnetic fields. In the inset, the 14 T and 1 T curves after subtraction of a linear background are represented to enhance the superconducting transition. adopted the In-Sn alloy as the standard to prepare the samples. During the critical current measurement, we routinely evaluated the contact resistance by measuring the voltage drops across the soldered junctions, i.e., between the tape and the sample holder or the resistive leads. These values obviously also need to take into account the contribution due to the resistive element. However, resistance values on the order of 100 n\(\Omega\) were commonly observed at liquid nitrogen temperatures, scaling well with the soldered area. This is coherent with the consideration that the main variable in play was the length of the tape soldered to the support. A drop of 30-50% was commonly observed in the liquid helium bath, allowing us to foresee heating due to joule effects in the range of tens/hundreds of mW at high currents. The obtained resistance values do not seem to represent an issue for measurements carried out in liquid helium baths, not even in the case of the flat sample holders characterized by shorter soldering areas and, thus, higher resistance. In Figure 9, we show a comparison of different measurements carried out on samples of Shanghai Technologies tapes mounted on different sample holders at different fields. It can be observed that no significant differences arose due to the fixture, either at high fields where the field orientation and transition localization could play a role in the mechanical stability or at lower fields where higher currents could lead to heating phenomena on shorter samples. It is worth highlighting that, already, the sample holder with the simplest design, i.e., the flat sample holder, which was characterized by ease of mounting and not needing long samples, was able to deliver good measurements characterized by a good SNR ratio in our experimental set-up. We take this factor as an indicator of the quality of the measurement, considering its dependence on several factors such as the tape's mechanical stability, the length of the probed region, and the voltage wires' stiffness.