Direct evidence for the occurrence of superconductivity in the magnetic compound YFe4Al8

For the first time we present direct evidence for superconductivity in the ternary magnetic compound YFe4Al8 with the ThMn12 type structure, found via point-contact (PC) experiments on contacts between a silver needle and single-crystal YFe4Al8, which reveal a distinct Andreev-reflection current. The spectra measured prove the existence of a normal–superconducting interface and exhibit a triangular-like shape in the vicinity of zero bias voltage, implying an unconventional type of superconductivity. The derived dependences of the order parameter versus temperature Δ(T) and magnetic field Δ(H) are presented. Δ(T) follows BCS theory, whereas Δ(H) does not satisfy any theoretical predictions. In some cases there exists noticeable superconductivity enhancement by a weak magnetic field. The data obtained imply a very inhomogeneous distribution of superconductivity over the sample volume in spite of its single-crystal structure. We assume that the reason is associated with inherent magnetic inhomogeneities of this material. The highest values for the critical temperature Tc, upper critical magnetic field Hc2, and ratio 2Δ(0)/kTc are 7.4 K, 5 T, and 7.2, respectively.