  The synthesis and properties of LiFeAs, a high-Tc 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(7) A and
c=6.364(2) A. 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 Tc=18 K with electronlike carriers and a
very high critical field, Hc2(0)>80 T. LiFeAs appears to be the chemical
equivalent of the infinite layered compound of the high-Tc cuprates.
