In the present work, diffraction of plane waves by an impedance half-plane in a cold plasma is investigated. A cold plasma may correspond to the ionosphere under the presence of the earth magnetic field where the effect of the finite tempreture and the pressurevariations are ignored. The antenna and wave propagation characteristics in the ionosphere-are important in satellite communication. An impedence half-plane in a cold plasma is a canonical configuration which may be used in modelling scattering from a variety of complex objects. The boundary-value problem corresponding to the canonical configuration is formulated by Fourier transform technique which leads to a matrix Wiener-Hopf equation. The kernel matrix is expressed in Daniele-Krapkov form which yields a rigorous solution to the problem under consideration. The field expressions can easily be obtained by the Standard saddle-point technique.