Security element

The unit has a characteristic region (12) e.g. imprinted machine readable barcode, selectively influencing a penetrated electromagnetic radiation, and containing a material with a photonic band gap. The characteristic region selectively absorbs the electromagnetic radiation in a narrow spectral range that lies in an ultraviolet spectral range. The characteristic region is colorless at a visible spectral range, and forms an optically variable layer, which is arranged towards an observer under different angle of vision of different color impressions. An independent claim is also included for a method for producing a security feature of a security unit, a security paper, a security foil and a data carrier.