We report on the longitudinal magnetoresistance (MR) in thin metal films on an Ising-type antiferromagnetic insulator, (). Steep changes in the MR spectra with hysteresis were observed at spin-flip transitions driven by magnetic fields applied along the easy axis of the crystal. The MR jumps almost follow step-like changes in magnetization at the spin-flip transition. At very low temperatures where moments are partially frozen, the MR anomalies exhibit a tunnel-magnetoresistance-like shape. The observed MR anomalies at the spin-flip transition are attributed to strain effects via magnetostriction upon the magnetic-structure change of the nets in , because similar MR jumps are observed in , , and heterostructures. Interestingly, we found that the high-field slopes of the MR spectra show opposite signs between and at low temperatures. Because similar MR spectra are observed for in which the interface magnetic interaction is negligible, the weak antilocalization due to the strong spin-orbit interaction of the Pt films is likely to contribute to the low-temperature MR.