Title: Tunable Weyl and Dirac states in the nonsymmorphic compound $\rm\mathbf{CeSbTe}$,
Abstract: Recent interest in topological semimetals has lead to the proposal of many
new topological phases that can be realized in real materials. Next to Dirac
and Weyl systems, these include more exotic phases based on manifold band
degeneracies in the bulk electronic structure. The exotic states in topological
semimetals are usually protected by some sort of crystal symmetry and the
introduction of magnetic order can influence these states by breaking time
reversal symmetry. Here we show that we can realize a rich variety of different
topological semimetal states in a single material, $\rm CeSbTe$. This compound
can exhibit different types of magnetic order that can be accessed easily by
applying a small field. It allows, therefore, for tuning the electronic
structure and can drive it through a manifold of topologically distinct phases,
such as the first nonsymmorphic magnetic topological material with an
eight-fold band crossing at a high symmetry point. Our experimental results are
backed by a full magnetic group theory analysis and ab initio calculations.
This discovery introduces a realistic and promising platform for studying the
interplay of magnetism and topology.