The theory of Andreev conductance is formulated for junctions involving normal metals (N) and multiband superconductors (S) and applied to the case of superconductors with nodeless extended $s_{pm}$-wave order parameter symmetry, as possibly realized in the recently discovered ferro pnictides. We find qualitative differences from tunneling into s-wave or d-wave superconductors that may help to identify such a state. First, interband interference leads to a suppression of Andreev reflection in the case of a highly transparent N/S interface and to a current deficit in the tunneling regime. Second, surface bound states may appear, both at zero and at non-zero energies. These effects do not occur in multiband superconductors without interband sign reversal, though the interference can still strongly modify the conductance spectra.
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