## Abstract

Measurements of the thermal and electrical conductivities of very pure lithium, sodium, potassium, rubidium and caesium have been made down to temperatures as low as 2 degrees K. The respective resistivities, W and $\rho $, may be written as the sum of an impurity resistance (W$_{0}$, $\rho _{0}$) and a so-called 'ideal' component (W$_{i}$, $\rho _{i}$) due to scattering by the thermal vibrations of the lattice. The terms in the thermal resistivity may be represented by W$_{0}$ = A/T and W$_{i}$ = BT$^{n}$ for T $\leq \theta $/10, where n $\simeq $ 2 and A = ($\rho _{0}$/2$\cdot $45) $\times $ 10$^{8}$ cm deg.$^{2}$ W$^{-1}$. Current theory predicts thatt he quantity C $\equiv $ B$\theta ^{2}$/W$_{\infty}$N$^{\frac{2}{3}}$ should be constant, where N is the number of free electrons per atom and W is the measured high-temperature resistivity. Taking N = 1, the present experiments yield C $\simeq $ 18 $\pm $ 4. The electrical resistance may be written $\rho $ = $\rho _{0}$ + $\beta $T$^{m}$ for T < $\theta $/10 with m $\simeq $ 5 except for sodium, where, below 8 degrees K, m is found to increase to 6. The theoretical relationships which exist between the low-temperature 'ideal' resistivities and those at higher temperatures are discussed in conjunction with the measured values. It is concluded that with the existing theories, no common adjustment of $\theta $ can give satisfactory agreement of theory with experiment. A new simple semi-empirical expression is put forward for W$_{i}$ which provides rather good agreement with experiment.