自從MgB2 在39 K 有超導特性的發現後，與其具有相同AlB2-type結構的化合物開始被廣泛討論，希望能夠成為有潛力的新型超導體.近年來，與MgB2有相同結構的層狀矽化物也因而再次被興趣地討論. 而除了AlB2-type結構之外，還存在另一個層狀矽化物系統，La2O3-type結構。在這次的研究中，我們將討論這兩個層狀矽化物系統：(1) YbGa1+xSi1−x系統 (2) Sr1−xYxAl2Si2系統。
我們利用核磁共振與Seeback係數量測來討論AlB2-type化合物YbGa1+xSi1−x的電子特性。這些材料的當前的價值在於其含有Yb元素卻有超導性的存在。從69Ga核磁共振自旋晶格鬆弛率的分析中，我們可推論這些材料的Ga 4s局部費米能階態密度Ns(EF)，而結果顯示隨著x值增加，Ns(EF)也隨之逐漸增加。此外經由量測Seebeck係數形貌的演變可以充分地了解能帶填滿的情況。從Seebeck係數的分析中，我們發現全部費米能階態密度N(EF)的變化與超導溫度Tc隨Ga值含量增加而逐漸減少的趨勢並不一致。這些觀測結果證實了電子費米能階態密度並非為定義超導温度的關鍵因素的假設。
為了能夠提供SrAl2Si2的電子特性與化學取代對其贋位能隙特徵的影響的微觀訊息，我們利用27Al核磁共振對Sr1−xYxAl2Si2 (x = 0, 0.05, 0.1, and 0.15)進行研究。對化學計量SrAl2Si2而言，溫度相關的NMR奈特位移與自旋晶格鬆弛率是與在費米能階周圍的贋位能隙中電子態密度的陡峭特徵有關連。另一方面，以Y取代的化合物顯現出普通的金屬行為，表示費米能階移出這些材料的贋位能隙，而這結果　　也在觀測出的鬆弛率遵守Korringa行為中得知。

Since superconductivity at Tc = 39 K was reported in MgB2, related compounds isostructural with AlB2-type structure have attracted much attention because of their potential as new superconductors. Recently, the layered silicides, isostructural to MgB2, have thus refocused interest. In addition to AlB2-type structure, there is another layered silicides system, the La2O3-type structure. In this study, we will discuss two layered silicides systems: (1) YbGa1+xSi1−x system, (2) Sr1−xYxAl2Si2 system.
We report the electronic properties of the AlB2-type compounds YbGa1+xSi1−x (x=0, 0.15, and 0.3) studied by means of the nuclear magnetic resonance (NMR) and the Seebeck coefficient measurements. These materials are of current interest due to the presence of superconductivity with Yb element. From the analysis of 69Ga NMR spin-lattice relaxation rates, we deduce the Ga 4s partial Fermi level density of states Ns(EF) for these compounds. The result indicates a gradual increase in Ns(EF) with increasing x in YbGa1+xSi1−x. In addition, the evolution of the Seebeck coefficient feature can be understood well within the band-filling scenario. From the Seebeck coefficient analysis, we find that the variation in the total Fermi level density of states N(EF)is not consistent with the trend of superconducting temperature Tc which shows a gradual decrease with Ga content. These observations support the hypothesis that the electronic Fermi level density of states is not the key factor in determining the superconducting transition temperature of YbGa1+xSi1−x.
Furthermore, with the aim of providing microscopic information about the electronic characteristics of SrAl2Si2 and effects of chemical substitution on its pseudogap features, we carried out a study on Sr1−xYxAl2Si2 (x = 0, 0.05, 0.1, and 0.15) by means of 27Al nuclear magnetic resonance (NMR) spectroscopy. For stoichiometric SrAl2Si2, the temperature-dependent NMR Knight shift and spin-lattice relaxation rate are associated with a sharp feature in the electronic density of state within a pseudogap at around the Fermi level. On the other hand, the NMR observations for Y-substituted compounds exhibit ordinary metallic behavior, suggesting that the Fermi level has moved out of the pseudogap for these materials, resulting in the dominant Korringa process responsible for the observed relaxation rates.

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