Achieving atomically flat and stoichiometric films of chiral antiferromagnets (AFM) with two-dimensional kagome spin lattice structures are crucial for integrating these materials in both established and emerging antiferromagnetic spintronic devices. We report a systematic study of growth and anomalous Hall effect in (111)-oriented noncollinear AFM ${\mathrm{Mn}}_{3+x}{\mathrm{Pt}}_{1-x}$ films with varying compositions, for $x=0.09$, 0.17, 0.28. Under optimized growth conditions, we obtain stoichiometric and atomically flat epitaxial ${\mathrm{Mn}}_3\mathrm{Pt}\left(111\right)$ films on Si(100) substrate, as evidenced by x-ray reflectivity and scanning probe microscopy. The magnetization measurement showed that epitaxial strain can induce a magnetic phase transition from an incommensurate spin state $\left(T_2\right)$ at $x=0.09$ to a triangular all-in/all-out AFM spin order $\left(T_1\right)$ at $x=0.17$, 0.28. The change in magnetic ground state is evident in the transport characteristics, as the $\left(T_1\right)$ state shows a robust intrinsic anomalous Hall effect (AHE) persisting to room temperature, in contrast to the $\left(T_2\right)$ state where AHE is negligible. Our studies reveal a hole-dominated conductance with room temperature anomalous Hall conductivity ranging from 5 to 16 ${\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$ for $x=0.17$ and 0.28, respectively. A scaling law is established, indicating that Hall resistivity is primarily governed by the intrinsic nonvanishing Berry curvature. The experimental observation corroborates the electronic structure calculations, which predicts the massless Dirac states near Fermi level in the bulk band structure, attributed to the presence of nonsymorphic glide symmetry. Additionally, we showed that chemical tuning via Mn doping can stabilize the required $T_1$ noncollinear AFM structure which enhance the topology driven intrinsic AHE.

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• Electronic structure
• First-principles calculations
• Magnetic phase transitions
• Magnetism
• Spin-orbit coupling
• Topological materials
• Epitaxy
• Film deposition