Electronic ground state of MnB$_{4}$
  Recent studies have dealt with the electronic and magnetic ground state properties of the tetraboride material MnB$_4$. So far, however, the ground state properties could not be established unambiguously. Therefore, here we present an experimental study on single-crystalline MnB$_4$ by means of resistivity and magnetization measurements. For this, we have developed a sample holder that allows four-point ac resistivity measurements on these very small ($\sim$\,100\,$\mu$m) samples. With our data we establish that the electronic ground state of MnB$_4$ is intrinsically that of a pseudo-gap system, in agreement with recent band structure calculations. Furthermore, we demonstrate that the material does neither show magnetic order nor a behavior arising from the vicinity to a magnetically ordered state, this way disproving previous claims. 
N.Steinki, J.L. Winter, D. Schulze Grachtrup, D. Menzel, S. S\"ullow,   A. Knappschneider, B. Albert
cond-mat.str-el cond-mat.mtrl-sci