  The model strongly correlated electron system Ho0.8Lu0.2B12 which
demonstrates a cooperative Jahn-Teller instability of the boron sub-lattice in
combination with rattling modes of Ho(Lu) ions, dynamic charge stripes and
unusual antiferromagnetic (AF) ground state has been studied in detail at low
temperatures by magnetoresistance, magnetization and heat capacity
measurements. Based on received results it turns out that the angular H-fi-T
magnetic phase diagrams of this non-equilibrium AF metal can be reconstructed
in the form of a Maltese cross. The dramatic AF ground state symmetry lowering
of this dodecaboride with fcc crystal structure can be attributed to the
redistribution of conduction electrons which leave the RKKY oscillations of the
electron spin density to participate in the dynamic charge stripes providing
with extraordinary changes in the indirect exchange interaction between
magnetic moments of Ho3+ ions and resulting in the emergence of a number of
various magnetic phases. It is also shown that the two main contributions to
magnetoresistance in the complex AF phase, the (i) positive linear on magnetic
field and the (ii) negative quadratic component can be separated and analyzed
quantitatively, correspondingly, in terms of charge carrier scattering on spin
density wave (5d) component of the magnetic structure and on local 4f-5d spin
fluctuations of holmium sites.

Strongly Correlated Electrons