Synthesis of New Lithium- and Monoamine-Intercalated Superconductors Li$_x$(C$_n$H$_{2n+3}$N)$_y$Fe$_{1-z}$Se ($n$ = 6, 8, 18) with the Dramatically Expanded Interlayer Spacing

New superconductors, Li$_x$(C$_n$H$_{2n+3}$N)$_y$Fe$_{1-z}$Se ($n$ = 6, 8, 18), have been synthesized via the co-intercalation of linear monoamines together with Li into FeSe. The distance between neighboring Fe layers expands up to 55.7 {AA} for n = 18, which is much larger than the previous record of 19 {AA} in the FeSe-based intercalation superconductors. Tc remains saturated at $sim$42 K.