[en] The materials CeSn₃, USn₃, and NpSn₃ are all moderately heavy Fermion compounds with electronic specific heat coefficients of 73, 169, and 242 mJ/mole K². CeSn₃ is known as a mixed valent system and NpSn₃ is a weak itinerant antiferromagnet. All three are strongly enhanced. Being in the relatively simple Au₃Cu structure, they form an excellent set of materials to study as representatives of strongly enhanced systems. One would like to ascertain what properties can be determined from band calculations based on density functional theory in the local density approximation. It has already been shown that the Fermi surface topology of CeSn₃ can be well described in this way even though the experimental masses are much larger than the band results. The enhancement factor for USn₃ is even larger and NpSN₃ is indeed predicted to go magnetic. We present here fully relativistic SCF calculations for these materials and discuss the relation between our results and what is known experimentally