We examine a novel phase of the underscreened Anderson lattice Model that might pertain to the "Hidden Ordered" phase of URu_2Si_2. We show that the system breaks spin-rotational invariance below the critical temperature and spontaneously selects a preferred axis of spin quantization. As a result, the low temperature phase exhibits a magnetic anisotropy, where the electronic properties depend not only on the magnitude of the magnetic field but also on the orientation of the applied field relative to the axis of quantization. The results are discussed in the context of recent experimental findings on URu_2Si_2.
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