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description of the exchange correlation potential [17]. 

Figure 1(c) shows momentum distributions curves (MDCs) of electrons emitted at E$_{F}$ as a function of k$_{x}$ ( ‖ ¯ Γ- ¯ M) for Sb(111). The out-of-plane component of the momentum k$_{z}$ was calculated for different incident photon energies ( hν ) using the free electron final state approximation with an experimentally determined inner potential of 14.5 eV [14]. There are four peaks in the MDCs centered about ¯ Γ that show no dispersion along k$_{z}$ and have narrow widths of Δ k$_{x}$ ≈ 0.03 ˚ A − $^{1}$. These are attributed to surface states and are similar to those that appear in Sb(111) thin films [14]. As hν is increased beyond 20 eV, a broad peak appears at k$_{x}$ ≈ -0.2 ˚ A − $^{1}$, outside the k range of the surface states near ¯ Γ, and eventually splits into two peaks. Such a strong k$_{z}$ disper- 

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sion, together with a broadened linewidth (Δ k$_{x}$ ≈ 0.12 ˚ A − $^{1}$), is indicative of bulk band behavior, and indeed these MDC peaks trace out a Fermi surface [Fig. 1(d)] that is similar in shape to the hole pocket calculated for bulk Sb near H [23]. Therefore by choosing an appropri- ate photon energy (e.g. ≤ 20 eV), the ARPES spectrum along ¯ Γ- ¯ M will have contributions from only the surface states. The small bulk electron pocket centered at L is not accessed using the photon energy range we employed [Fig. 1(d)]. 

ARPES spectra along ¯ Γ- ¯ M taken at three different pho- ton energies are shown in Fig. 2. Near ¯ Γ there are two rather linearly dispersive electron like bands that meet exactly at ¯ Γ at a binding energy E$_{B}$ ∼ -0.2 eV. This be- havior is consistent with previous ARPES measurements along the ¯ Γ- ¯ K direction [13] and is thought to come from a pair of spin-split surface bands that become degener- ate at the time reversal invariant momentum (TRIM) ¯ Γ due to Kramers degeneracy. The Fermi velocities of the inner and outer V-shaped bands are 4 . 4 ± 0 . 1 eV · ˚ Aand 2 . 2 ± 0 . 1 eV · ˚ Arespectively as found by fitting straight lines to their MDC peak positions. The surface origin of this pair of bands is established by their lack of depen- dence on hν [Fig. 2(a)-(c)]. A strongly photon energy dispersive hole like band is clearly seen on the negative k$_{x}$ side of the surface Kramers pair, which crosses E$_{F}$ for hν = 24 eV and gives rise to the bulk hole Fermi surface near H [Fig. 1(d)]. For hν ≤ 20 eV, this band shows clear back folding near E$_{B}$ ≈ -0.2 eV indicating that it has completely sunk below E$_{F}$ . Further evidence for its bulk origin comes from its close match to band cal- culations [Fig. 2(a)]. Interestingly, at photon energies such as 18 eV where the bulk bands are far below E$_{F}$ , there remains a uniform envelope of weak spectral inten- 

