Antiferromagnets have attracted extensive attention in spintronics and valleytronics due to their intrinsic advantages, including the absence of stray field and ultrafast dynamics. However, the lack of spin splitting in conventional antiferromagnets severely limits their spintronic applications, particularly the realization of the anomalous valley Hall effect (AVHE). To overcome this limitation, we propose a general strategy by constructing an interlayer $A$-type antiferromagnetic (AFM) bilayer from a ferromagnetic (FM) valley-polarized monolayer. An out-of-plane electric field is applied to break the combined spatial inversion and time reversal $\widehat{P}\widehat{T}$ symmetry, thereby inducing spin splitting and enabling the AVHE. To validate this paradigm and provide a concrete material platform, we perform first-principles calculations to systematically investigate the spin-valley physics of monolayer and bilayer $\mathrm{Gd}{\mathrm{I}}_2$. The monolayer is FM, while the AB1-stacked bilayer stabilizes in an interlayer $A$-type AFM state without spin splitting. Both systems display strong intrinsic valley polarization, with valley splittings of 145.9 and 140.2 meV for the monolayer and bilayer, respectively; both values are sufficient to support room-temperature valleytronic applications. For bilayer $\mathrm{Gd}{\mathrm{I}}_2$, even a tiny out-of-plane electric field breaks the $\widehat{P}\widehat{T}$ symmetry, inducing the full-Brillouin-zone spin splitting and enabling the AVHE, while the interlayer AFM coupling and valley splitting remain robust. As the electric field increases further (exceeding $0.04\mathrm{V}/\AA$), an interlayer AFM-to-FM transition occurs, accompanied by an enhancement of the valley splitting due to the strengthened spin-orbit coupling. All of the above phenomena have also been demonstrated in bilayer $\mathrm{Y}{\mathrm{I}}_2$. These results not only deepen the understanding of spin-valley coupling in layered AFM systems but also highlight a universal paradigm for designing AFM bilayer systems with controllable spin splitting, valley splitting, and the AVHE.

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• Electronic structure
• Magnetism
• Valley degrees of freedom
• Valleytronics
• Antiferromagnets
• First-principles calculations