  LumiCal is a sampling electromagnetic calorimeter designed for the precise
measurement of integrated luminosity in electron positron linear collider
experiments. The present report contains a description and results of the first
beam test of a multilayer LumiCal prototype with four silicon detector planes.
A 5 GeV electron beam from the CERN PS T9 facility was used to study the
performance of the LumiCal prototype. Presented results are mainly focused on
the transverse structure of the observed electromagnetic shower and the
Moli\`ere radius measurement. A comparison with MC simulation is also
discussed.
