We investigate single crystals of the trigonal antiferromagnet Formula Presented (Formula Presented) by means of electrical transport, magnetization measurements, x-ray magnetic scattering, optical reflectivity, angle-resolved photoemission spectroscopy (ARPES), and ab initio band structure calculations (Formula Presented). We find that the electrical resistivity of Formula Presented increases strongly upon cooling and can be suppressed in magnetic fields by several orders of magnitude (colossal magnetoresistance effect). Resonant magnetic scattering reveals a magnetic ordering vector of Formula Presented, corresponding to an Formula Presented-type antiferromagnetic order, below Formula Presented. We find that the moments are canted out of the Formula Presented plane by an angle of about Formula Presented and aligned along the [100] direction in the Formula Presented plane. We observe nearly isotropic magnetization behavior for low fields and low temperatures which is consistent with the magnetic scattering results. The magnetization measurements show a deviation from the Curie-Weiss behavior below Formula Presented, the temperature below which also the field dependence of the material's resistivity starts to increase. An analysis of the infrared reflectivity spectrum at Formula Presented allows us to resolve the main phonon bands and intraband and interband transitions, and estimate indirect and direct band gaps of Formula Presented and Formula Presented, respectively, which are in good agreement with the theoretically predicted ones. The experimental band structure obtained by ARPES is nearly Formula Presented independent above and below Formula Presented. The comparison of the theoretical and experimental data shows a weak intermixing of the Eu Formula Presented states close to the Formula Presented point with the bands formed by the phosphorous Formula Presented orbitals leading to an induction of a small magnetic moment at the P sites.