gemeinschaft through the framework SFB 463. [1] R.J. Cava, H. Zandbergen, B. Batlogg, H. Eisaki, H. Takagi, J.J. Krajewski, W.F. Peck, E. Gyorgy, and S. Uchida, Nature 372 , 245 (1994). [2] R.J. Cava, B. Batlogg, T. Siegrist, J.J. Krajewski, W.F. Peck, S. Carter, R.J. Felder, H. Takagi, and R.B. vanDover, Phys.Rev.B 49 , 12384 (1994). [3] T. Siegrist, H. Zandbergen, R.J. Cava, J. Krajewski, and W.F. Peck, Nature 367 , 254 (1994). [4] T. Siegrist, R.J. Cava, J. Krajewski, and W.F. Peck, J.Alloys Comp. 216 , 135 (1994). [5] K. Muller and V. Narozhnyi, Reports on Progress in Physics 64 , 943 (2001). [6] P. Thalmeier and G. Zwicknagl, in Handbook on the Physics and Chemistry of Rare Earths , edited by K. Gschneidner Jr., J.-C. B¨ unzli, and V. Pecharsky (Elsevier B.V., 2005), vol. 34, chapt. 219. [7] C. Mazumdar and R. Nagarajan, Current Science 88 , 83 (2005). [8] K.H. M¨ uller, M. Schneider, G. Fuchs, and S.L. Drechsler, in Handbook on the Physics and Chemistry of Rare Earths , edited by K. Gschneidner Jr., J.-C. B¨ unzli, and V. Pecharsky (Elsevier B.V., 2008), vol. 38, chapt 239. [9] L. Mattheiss, Solid State Communications 94 , 741 (1995). [10] S.L. Bud’ko and P.C. Canfield, Comptes Rendus Physique 7 , 56 (2006). [11] G. Behr, W. L¨ oser, D. Souptel, G. Fuchs, I. Mazilu, C. Cao, A. K¨ ohler, L. Schultz, and B. B¨ uchner, J.Cryst.Growth 310 , 2268 (2008). [12] D. Souptel, G. Behr, A. Kreyssig, and W. L¨ oser, J.Cryst.Growth 276 , 652 (2005). [13] B. Bergk, O. Ignatchik, A. Bianchi, M. Jaeckel, J. Wosnitza, J. Perenboom, and P. Canfield, Physica C 460 , 630 (2007). [14] Y. Naidyuk, D. Bashlakov, I. Yanson, G. Fuchs, G. Behr, D. Souptel, and S. Drechsler, Physica C 460 , 103 (2007). [15] N. Bobrov, V. Chernobay, Y. Naidyuk, L. Tyutrina, D. Naugle, K. Rathnayaka, S. Bud’ko, P. Canfield, and I. Yanson, Epl 83 , (2008). [16] M. Schneider, A. Gladun, A. Kreyssig, J. Wosnitza, V. Petzold, H. Rosner, G. Behr, D. Soup- tel, K. M¨ uller, S. Drechsler, et al., J.Phys.: Cond.Matter 20 , (2008). [17] S. Arisawa, T. Hatano, K. Nakamura, and K. Togano, Physica C 308 , 67 (1998). 12