follows. In § 2, we analyze the buckling of sheets of B and C atoms. In § 3, we briefly summarize the formulae used in the calculation of the RXS spectra. In § 4, we calculate the RXS spectra on two mechanisms. Section 5 is devoted to concluding remarks.

Lattice Distortion
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![ Sketch of a B$_2$C$_2$ sheet ($z=c/2$). Open circles represent B and C atoms; big and small circles move to positive and negative directions along the $z$ axis, respectively. The directions are reversed on the plane of $z=-c/2$. Hatched circles represent Dy atoms at the plane of $z=0$. \[fig.distortion\]](fig.print.2.eps){width="8.0cm"}

For making clear the effect of lattice distortion on electronic states, we first calculate the electrostatic potential on the basis of a point charge model. [@Hutchings] Point charges $q_{Dy}$, $q_B$, and $q_C$ are placed on Dy, B, and C sites, respectively. Figure \[fig.distortion\] shows the positions of B and C atoms on the plane of $z=c/2$ and those of Dy atoms on the plane of $z=0$. For the buckling of sheets of B and C atoms (up- and down-movements along the $c$ axis) specified in Fig. \[fig.distortion\], the electrostatic potential is evaluated within the second order of coordinates around 