Anisotropic thermodynamic and transport properties of single-crystalline CaKFe sub(4) As sub(4)

(ProQuest: ... denotes formulae and/or non-USASCII text omitted) Single-crystalline, single-phase CaKFe sub(4) As sub(4) has been grown out of a high-temperature, quaternary melt. Temperature-dependent measurements of x-ray diffraction, anisotropic electrical resistivity, elastoresistivity, thermoelectric power, Hall effect, magnetization, and specific heat, combined with field-dependent measurements of electrical resistivity and field and pressure-dependent measurements of magnetization indicate that CaKFe sub(4) As sub(4) is an ordered, stoichiometric, Fe-based superconductor with a superconducting critical temperature, T sub(c)=35.0+ or -0.2 K. Other than superconductivity, there is no indication of any other phase transition for 1.8K[< or =]T[< or =]300 K. All of these thermodynamic and transport data reveal striking similarities to those found for optimally or slightly overdoped (Ba sub(1-x) K sub(x))Fe sub(2) As sub(2), suggesting that stoichiometric CaKFe sub(4) As sub(4) is intrinsically close to what is referred to as "optimal-doped" on a generalized, Fe-based superconductor, phase diagram. The anisotropic superconducting upper critical field, H sub(c 2)(T), of CaKFe sub(4) As sub(4) was determined up to 630 kOe. The anisotropy parameter ... applied perpendicular and parallel to the c axis, decreases from [Asymptotically = to]2.5 at T sub(c) to [Asymptotically = to]1.5 at 25 K, which can be explained by interplay of paramagnetic pair breaking and orbital effects. The slopes of ... kOe/K and ... kOe/K at T sub(c) yield an electron mass anisotropy of m[perpendicular]/m sub(||) [Asymptotically = to]1/6 and short Ginzburg-Landau coherence lengths [xi] sub(||)(0)[Asymptotically = to]5.8A and [xi] sub([perpendicular])(0)[Asymptotically = to]14.3A. The value of ... can be extrapolated to [Asymptotically = to]920 kOe, well above the BCS paramagnetic limit.