We say that a set Ω⊆Rn\documentclass[12pt]{minimal}
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\begin{document}$$\Omega \subseteq {\mathbb {R}}^n$$\end{document} with positive Lebesgue measure is a spectral set if L2(Ω)\documentclass[12pt]{minimal}
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\begin{document}$$L^{2}(\Omega )$$\end{document} admits an orthogonal basis of exponentials. In this paper, we study the spectrality of self-affine tiles. We prove a class of sets T:=T(M,D)\documentclass[12pt]{minimal}
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\begin{document}$$T:=T(M,D)$$\end{document} with positive Lebesgue measure satisfying MT=⋃d∈D(T+d)\documentclass[12pt]{minimal}
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\begin{document}$$MT=\bigcup _{d\in D}(T+d)$$\end{document} are spectral sets, where M∈M2(Z)\documentclass[12pt]{minimal}
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\begin{document}$$M\in M_{2}({\mathbb {Z}})$$\end{document} is an expanding matrix with |det(M)|=4\documentclass[12pt]{minimal}
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\begin{document}$$|\det {(M)}|=4$$\end{document} and D={0,α,β,-(α+β)}⊂Z2\documentclass[12pt]{minimal}
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\begin{document}$$D=\{{\textbf{0}},\mathbf {\alpha },\beta ,-(\alpha +\beta )\}\subset {\mathbb {Z}}^2$$\end{document} is a non-collinear digit set. As an application, we conclude that T is a spectral set if and only if it tiles R2\documentclass[12pt]{minimal}
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\begin{document}$${\mathbb {R}}^2$$\end{document} by translations.