  New iron selenide superconductors by intercalating smaller-sized alkali
metals (Li, Na) and alkaline earths using high-temperature routes have been
pursued ever since the discovery of superconductivity at about 30 K in KFe2Se2,
but all have failed so far. Here we demonstrate that a series of
superconductors with enhanced Tc=30~46 K can be obtained by intercalating
metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the
ammonothermal method at room temperature. Analysis on their powder X-ray
diffraction patterns reveals that all the main phases can be indexed based on
body-centered tetragonal lattices with a~3.755-3.831 {\AA} while c~15.99-20.54
{\AA}. Resistivities show the corresponding sharp transitions at 45 K and 39 K
for NaFe2Se2 and Ba0.8Fe2Se2, respectively, confirming their bulk
superconductivity. These findings provide a new starting point for studying the
properties of these superconductors and an effective synthetic route for the
exploration of new superconductors as well.
