  A new iron-based superconductor, Lix(C6H16N2)yFe2-zSe2, with Tc = 38 K has
successfully been synthesized via the intercalation of lithium and
hexamethylenediamine into FeSe. The superconducting transition has been
confirmed not only by magnetic susceptibility measurements but also by
electrical resistivity ones. The interlayer spacing, namely, the dicstance
between neighboring Fe layers, d, is 16.225(5) $\mathring{\text{A}}$, which is
the largest among those of FeSe-based intercalation compounds. It has been
found that the dependence of Tc on d in FeSe-based intercalation
superconductors appears domic.
