Fluctuation conductivity in superconducting MgB$_{2}$

According to the crystal structure of MgB$_{2}$ and band structure calculations quasi-two-dimensional (2D) boron planes are responsible for the superconductivity. We report on critical field and resistance measurements of 5.6 $\mu$m thick MgB$_{2}$ films grown on a sapphire single crystalline substrate. Resistivity measurements yield a temperature dependence of the fluctuation conductivity above the critical temperature which agrees with the Aslamazov–Larkin and Maki-Thompson theory of fluctuations in layered superconductors, indicating a quasi-two-dimensional nucleation of superconductivity in MgB$_{2}$.