Abstract

Stannides with crystal structures composed of rigid covalently bonded frameworks forming cages filled with guest atoms exhibit an astonishing diversity of interesting behaviours that are, moreover, accessible to tuning. Recent reports on unconventional superconducting states and intriguing structural and electronic instabilities for compounds with skutterudite-related crystal structures and the stoichiometry M3T4 Sn13 (M is a rare earth or alkaline earth; T is a transition metal)[1-4] prompted us to study consecutive members of this family.

In this talk, I will introduce a novel superconductor Ca3+xCo4Sn13-x (x  0.2) with TC  5.5 K and a huge low temperature normal state magnetoresistance (MR) of up to 1000% in magnetic field of 9 T for crystals grown from Sn flux with the residual resistivity ratio (RRR) of 64. I will demonstrate that the magnitude of MR scales with the RRR , MR  1.6(1) RRR1 .7(2). I will present results of structural, thermodynamic and transport measurements. With the help of the experimental data and electronic band structure results I will address the origin of the extraordinarily large MR and the role of multiband effects in Ca3.2Co4Sn12.8.

In the second part of the talk, I will discuss the ways of tuning the physical properties of the M3T4 Sn13 -type systems in the context of their electronic band structure and chemical bonding characteristics based on examples of {La,Ce}3Rh4Sn13 and Ca3Co4Sn13.

[1] S. K. Goh et al., Phys. Rev. Lett. 114, 097002 (2015) and references therein [2] A. Ślebarski et al., Phys. Rev. B 89 , 125111 (2014) and references therein [3] N. Kase, H. Hayamizu, and J. Akimitsu, Phys. Rev. B 83 , 184509 (2011) [4] P. D. Kulkarni et al., Phys. Rev. B 84 , 014501 (2011) and references therein