We have investigated the magnetic susceptibility, the electrical resistivity, the specific heat, the thermoelectric power, the Hall coefficient, and the thermal conductivity of the ${\text{Al}}_{13}{\text{Fe}}_4$ and ${\text{Al}}_{13}{\left(\text{Fe},\text{Ni}\right)}_4$ monoclinic approximants to the decagonal quasicrystal. While the ${\text{Al}}_{13}{\text{Fe}}_4$ crystals are structurally well ordered, the ternary derivative ${\text{Al}}_{13}{\left(\text{Fe},\text{Ni}\right)}_4$ contains substitutional disorder and is considered as a disordered version of the ${\text{Al}}_{13}{\text{Fe}}_4$. The crystallographic-direction-dependent measurements were performed along the $a^{\ast }$, $b$, and $c$ directions of the monoclinic unit cell, where the $\left(a^{\ast },c\right)$ atomic planes are stacked along the $b$ direction. The electronic transport and the magnetic properties exhibit significant anisotropy. The stacking $b$ direction is the most conducting direction for the electricity and heat. The effect of substitutional disorder in ${\text{Al}}_{13}{\left(\text{Fe},\text{Ni}\right)}_4$ is manifested in the large residual resistivity $\rho \left(T\to 0\right)$ and significantly reduced thermal conductivity of this compound, as compared to the ordered ${\text{Al}}_{13}{\text{Fe}}_4$. Specific-heat measurements reveal that the electronic density of states at the Fermi level of both compounds is high. The anisotropic Hall coefficient $R_H$ reflects complex structure of the anisotropic Fermi surface that contains electronlike and holelike contributions. Depending on the combination of directions of the current and the magnetic field, electronlike $\left(R_H<0\right)$ or holelike $\left(R_H>0\right)$ contributions may dominate, or the two contributions compensate each other $\left(R_H\approx 0\right)$. Similar complicated anisotropic behavior was observed also in the thermopower. The anisotropic Fermi surface was calculated ab initio using the atomic parameters of the refined ${\text{Al}}_{13}{\text{Fe}}_4$ structural model that is also presented in this work.

• Received 3 November 2009

DOI:https://doi.org/10.1103/PhysRevB.81.184203