  We investigate the superconducting behaviour of Bi doped Pb. Pure lead shows
type-I behaviour entering an intermediate state in a magnetic field. High
dopings of Bi ($>$3%) lead to type-II behaviour showing a mixed state, where
the magnetic field penetrates the superconductor in the form of a flux lattice.
At intermediate doping, the sample shows both type-I and type-II behaviour
depending on the temperature. This arises because the Ginzburg-Landau parameter
$\kappa$ passes through its critical value of $1/\sqrt{2}$ with temperature.
