  We report on an improved test of the Universality of Free Fall using a
rubidium-potassium dual-species matter wave interferometer. We describe our
apparatus and detail challenges and solutions relevant when operating a
potassium interferometer, as well as systematic effects affecting our
measurement. Our determination of the E\"otv\"os ratio yields
$\eta_{\,\text{Rb,K}}=-1.9\times10^{-7}$ with a combined standard uncertainty
of $\sigma_\eta=3.2\times10^{-7}$.
