  We use a magnetothermal resistance method to measure lattice thermal
conductivity of pure single crystal metals over a wide range of temperatures.
Large transverse magnetic fields are applied to suppress electronic thermal
conduction. The total thermal conductivity and the electrical conductivity are
measured as functions of applied magnetic field. The lattice thermal
conductivity is then extracted by extrapolating the thermal conductivity versus
electrical conductivity curve at zero electrical conductivity. We used this
method to experimentally measure the lattice thermal conductivity and Lorenz
number in single crystal Al (100), Cu (100) and Zn (001) in a temperature range
of 5 to 60 K. Our results show that the measured phonon thermal conductivity
versus temperature plot has a peak around one tenth of the Debye Temperature,
and the Lorenz number is found to deviate from the Sommerfeld value in the
intermediate temperature range.
