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We have investigated anisotropic physical properties (the magnetic susceptibility, the electrical resistivity, the thermoelectric power, the Hall coefficient and the thermal conductivity) of the single-crystalline Taylor-phase T-Al72.5Mn21.5Fe6.0 complex intermetallic that is an orthorhombic approximant to the d-Al-Mn-Pd decagonal quasicrystal. The measurements were performed along the a, b, and c directions of the orthorhombic unit cell, where (a, c) atomic planes are stacked along the perpendicular b direction. The T-Al72.5Mn21.5Fe6.0 shows spin-glass behavior below the spin-freezing temperature T-f approximate to 29 K with a small anisotropy in the magnetic susceptibility. The anisotropic electrical resistivities are rather large and show negative temperature coefficient. The resistivity is lowest along the stacking direction, which appears to be a common property of the decagonal-approximant phases with a stacked-layer structure. The temperature-dependent resistivity was theoretically reproduced by the quantum transport theory of slow charge carriers. The thermopower is positive for all three crystallographic directions, indicating that holes are the majority charge carriers, and no anisotropy can be claimed within the experimental precision. The same conclusion on the holes being the dominant charge carriers follows from the Hall-coefficient measurements, which is a sum of the (positive) normal Hall coefficient and the anomalous term, originating from the magnetization. The anisotropy of the thermal conductivity is practically negligible. The T-Al72.5Mn21.5Fe6.0 Taylor phase can be considered as a "close-to-isotropic" complex intermetallic. The relation of the anisotropic physical properties of the Taylor phase to other families of decagonal-approximant phases with the stacked-layer structure is discussed.

Two stable quasicrystalline approximants in the Al-Cr-Fe system-a gamma-brass phase ( -AlCrFe) and a mixture of two orthorhombic approximants of the decagonal phase (O1/O2-AlCrFe)-were investigated by magnetic susceptibility, electrical resistivity, thermal conductivity and thermoelectric power measurements, combined with structural investigations by X-ray diffraction, light microscopy (LM) and scanning electron microscopy (SEM). The investigated approximants exhibit physical properties that are in many respects intermediate to regular metals and quasicrystals (QCs). Their electrical resistivities show very weak temperature dependences and the resistivity values are in between regular metals and Al-based QCs. The magnetic susceptibility results show the existence of a small fraction (of about 1 % for the -AlCrFe and about ten times less for the O1/O2-AlCrFe) of localized magnetic moments with Curie-like temperature dependence. Thermal conductivity measurements show that the electronic and lattice contributions are of comparable size. While the electronic contribution can be described by the Wiedemann-Franz law, the lattice contribution can be reproduced by a sum of a Debye (long-wavelength phonons) and fracton hopping terms. At the lowest measured temperature (8 K), scattering of phonons on stacking-faults-like defects limits the heat transport, where this type of defects has also been observed in the LM and SEM structural investigations. The presented results indicate that the magnetic and transport physical properties of quasicrystalline approximants are not determined by the short-range atomic order only, but are affected by both, the short-range quasiperiodic and long-range periodic atomic orders.