Rhombohedral-boron carbide (r-BxC) forms crystal structures where B12 or B11C icosahedra are connected by triatomic chains forming a 3D network with strong covalent B-B and B-C bonding, typically rendering the stoichiometry B4C or B13C2. This crystal structure makes boron carbide very hard and it is typically used in plate armor and as an abrasive material. The high boron content and high mechanical and chemical stability have also made BxC a promising candidate for neutron converter layers in solid-state neutron detectors where B converts neutrons to detectable particles. Less explored are the optoelectronic and the thermoelectric properties of r-BxC, the wide range of composition and material stability make the material promising also for radiation-resistant heterostructures and thermoelectric devices respectively. To enable the use of r-BxC in such devices, there is a need to develop and understand thin film deposition processes for high-quality, phase pure epitaxial r-BxC films.