  Transition metal compounds with kagome structure have been found to exhibit a
variety of exotic structural, electronic, and magnetic orders. These orders are
competing with energies very close to each other, resulting in complex phase
transitions. Some of the phases are easily observable, such as the charge
density wave (CDW) and the superconducting phase, while others are more
challenging to identify and characterize. Here we present magneto-transport
evidence of a new phase below ~35 K in the kagome topological metal
CsV$_3$Sb$_5$ (CVS) thin flakes between the CDW and the superconducting
transition temperatures. This phase is characterized by six-fold rotational
symmetry in the in-plane magnetoresistance (MR) and is connected to the orbital
current order in CVS. Furthermore, the phase is characterized by a large
in-plane negative magnetoresistance, which suggests the existence of a
three-dimensional, magnetic field-tunable orbital current ordered phase. Our
results highlight the potential of magneto-transport to reveal the interactions
between exotic quantum states of matter and to uncover the symmetry of such
hidden phases.
