We have studied the half-Heusler compound TbPdBi through resistivity, magnetization, Hall effect, and heat capacity measurements. A semimetal behavior is observed in its normal-state transport properties, which is characterized by a large negative magnetoresistance below 100 K. Notably, we find the coexistence of superconductivity and antiferromagnetism in this compound. The superconducting transition appears at 1.7 K, while the antiferromagnetic phase transition takes place at 5.5 K. The upper critical field Hc2 shows an unusual linear temperature dependence, implying unconventional superconductivity. Moreover, when the superconductivity is suppressed by magnetic field, its resistivity shows plateau behavior, a signature often seen in topological insulators/semimetals. These findings establish TbPdBi as a platform for the study of the interplay between superconductivity, magnetism, and nontrivial band topology. \ 2018 American Physical Society.