<p>First, a novel Fe-Co/Al-Si composite is fabricated by a casting method and subjected to reheating to form an interfacial reaction layer between the Fe-Co wire and Al-Si matrix. Eight composites with different interfacial reaction layers are prepared by varying the reheating conditions (reheating time and reheating temperature). Second, an energy harvesting device comprising an Fe-Co/Al-Si composite specimen, two magnets, and a coil is prepared. Subsequently, the induced voltage originating from the developed devices is measured using an in-house impact energy harvesting test system. The energy harvesting performance is calculated from the result of induced voltage under impact loading. The interfacial shear stress between the Fe-Co wire and Al-Si matrix is also measured by subjecting the composites to a pull-out test. The interfacial shear deformation resistance is then calculated from the result of the interfacial shear stress. The results reveal that the slight formation of the interfacial reaction layer enhances the energy harvesting performance, but the growth of the interfacial reaction layer degrades this performance. In contrast, the interfacial shear deformation resistance undergoes a substantial increase as a consequence of the formation of the zigzag interfacial reaction layer. This phenomenon is attributed to the anchor effect.</p>