Physical properties of the quasicrystal YbCd5.7 and its approximant YbCd6

We have measured the magnetization, low-temperature heat capacity and electrical resistivity of the binary quasicrystal YbCd5.7 and its crystalline approximant, cubic YbCd6. Magnetization data reveal that Yb ions are divalent in both compounds. The coefficient of the linear term in the heat capacity, γ, is 51 and 7.5 mJ mol-1 K-2 in YbCd6 and YbCd5.7, respectively. The heat capacity data thus reveal a significant reduction in the electronic density of states in the quasicrystalline phase. However, the Debye temperatures of the two compounds are comparable; 144 and 138 K, respectively. The electrical resistivity of YbCd6 shows typical metallic behaviour while the resistivity of YbCd5.7, larger than that of YbCd6, is characterized by a negative temperature coefficient below 300 K with a peak around 50 K. (author)