The electrical resistivity of soft solder (Pb_0.28Sn_0.72) has been measured in the temperature range 4.2 K to 300 K. The ‘alloy’ becomes electrically superconducting at a temperature of 6.9 K. Above this, in the entire temperature range, the resistivity could be described, apart from the residual resistivity, by the weighted average of the resistivities of the individual constituents which are derived from the Bloch-Grüneisen relation. The results are in accordance with the phase diagram, which shows a co-existence of two phases in almost the entire range of concentration of the Pb-Sn binary system. It has been shown that the thermal conductivity data on soft solder as well as on Pb_0.7Sn_0.3, both taken from literature, could be interpreted on the same basis, below and above the ‘superconducting transition temperature’. Recent results on other Pb-Sn systems are discussed in the light of this interpretation.

Titanium-rich transition metal alloys are metastable in their quenched boc β phase. The instability is relieved by low temperature structural transformations. We have investigated this in a series of Ti-Nb alloys, through the measurements of electrical resistivity (ρ), superconducting transition temperature and upper critical field. Supporting structural evidence has been obtained from transmission electron microscopy (tem) and x-ray studies. It is shown that both ρ and dρ/dT can be used as useful indices of this instability. The enhanced value of resistivity on account of the instability results in the enhancement of upper critical field as shown from dH_c2/dT measurements.