Structural and superconducting properties of MgB${}_{2-x}$Be${}_x$

We prepared MgB${}_{2-x}$Be${}_x$ ($x=0$, 0.2, 0.3, 0.4, and 0.6) samples where B is substituted with Be. MgB${}_2$ structure is maintained up to $x=0.6$. In-plane and inter-plane lattice constants were found to decrease and increase, respectively. Superconducting transition temperature $T_c$ decreases with $x$. We found that the $T_c$ decrease is correlated with in-plane contraction but is insensitive to carrier doping, which is consistent with other substitution studies such as Mg${}_{1-x}$Al${}_x$B${}_2$ and MgB${}_{2-x}$C${}_x$. Implication of this work is discussed in terms of the 2D nature of $\sigma$-band.