The synthesis and properties of LiFeAs, a high-$T_c$ Fe-based superconducting stoichiometric compound, are reported. Single crystal x-ray studies reveal that it crystallizes in the tetragonal PbFCl type (P4/nmm) with $a=3.7914\left(7\right)\text{Å}$ and $c=6.364\left(2\right)\text{Å}$. Unlike the known isoelectronic undoped intrinsic FeAs compounds, LiFeAs does not show any spin-density wave behavior but exhibits superconductivity at ambient pressures without chemical doping. It exhibits a respectable transition temperature of $T_c=18\text{K}$ with electronlike carriers and a very high critical field, ${\text{H}}_{c2}\left(0\right)>80\text{T}$. LiFeAs appears to be the chemical equivalent of the infinite layered compound of the high-$T_c$ cuprates.

• Received 23 July 2008

DOI:https://doi.org/10.1103/PhysRevB.78.060505