  Electrons navigate more easily in a background of ordered magnetic moments
than around randomly oriented ones. This fundamental quantum mechanical
principle is due to their Bloch wave nature and also underlies ballistic
electronic motion in a perfect crystal. As a result, a paramagnetic metal that
develops ferromagnetic order often experiences a sharp drop in the resistivity.
Despite the universality of this phenomenon, a direct observation of the impact
of ferromagnetic order on the electronic quasiparticles in a magnetic metal is
still lacking. Here we demonstrate that quasiparticles experience a significant
enhancement of their lifetime in the ferromagnetic state of the low-density
magnetic semimetal EuCd2As2, but this occurs only in selected bands and
specific energy ranges. This is a direct consequence of the magnetically
induced band splitting and the multi-orbital nature of the material. Our
detailed study allows to disentangle different electronic scattering mechanisms
due to non-magnetic disorder and magnon exchange. Such high momentum and energy
dependence quasiparticle lifetime enhancement can lead to spin selective
transport and potential spintronic applications.
