Match scores (Hove)
Somerset win by 9 runs (D/L Method)
Somerset inns (49 overs): 303-5 (Elgar 131, Hose 76; Wiese 2-51)
Sussex inns (20 overs): 155-9 (Evans 40; Overton 3-21)
Match report
Dean Elgar became the second Somerset batsman to score an unbeaten century in this season's Royal London One-Day Cup as his side beat Sussex by nine runs under the Duckworth/Lewis method at Hove.
Elgar made an unbeaten 131, his highest List A score, in Somerset's 303 for five from 49 overs two days after Roelof van der Merwe had smashed 165 not out in the win over Surrey.
Chasing 165 in 20 overs after two rain delays, Sussex finished on 155 for nine.
Somerset, who were put in, had been 120 for four in the 27th over before Adam Hose joined South African Elgar to transform the innings in a partnership of 151 in 20 overs.
Elgar scored his runs off 127 balls with 10 fours and four sixes while Hose contributed 76 from just 58 deliveries with five fours and three sixes as Somerset plundered 96 off the last nine overs before the first stoppage.
Such a promising scenario had seemed unlikely earlier when Somerset completed the first 10-over powerplay on 42 for two.
Steven Davies, who has struggled for runs since his move from Surrey, sliced the fourth ball of the innings from David Wiese to backward point and the seamer claimed a second victim in the ninth over when Peter Trego (20) inside-edged and was caught behind.
James Allenby lost middle and off stumps aiming to leg in the 15th over to give left-armer George Garton his first of two wickets but Elgar then began to take control, first in partnership with James Hildreth with whom he put on 61 in 12 overs.
Hildreth (24) looked in good touch until he was deceived by a quicker ball from slow left-armer Danny Briggs but thereafter Elgar and Hose were in complete control.
Elgar's first six off Briggs took him into the 90s before a quickly taken single brought up his fifth List A hundred from 107 balls.
By now Hose was finding his range too. The seven sixes plundered by the pair were all deposited in an area between midwicket and long leg as they took advantage of a short boundary.
Hose was dropped on 65 at long leg by Chris Nash and was in sight of beating his previous List A best of 77, made against Essex last season, when he holed out to wide long on.
That brought Van der Merwe to the crease and he was quickly into his stride, clearing the midwicket rope with his second and fourth scoring shots, both off Wiese, in a cameo of 15 from eight balls to lift Somerset above 300.
Sussex's reply got off to the worst possible start when Nash was caught at short fine leg off the first ball from Craig Overton.
Harry Finch (25) and Luke Wright took the visitors to 49 before Van der Merwe made an impact with his slow left-arm spin. His quicker delivery bowled Finch first ball and he had Ben Brown lbw in his third over.
Wright (28) holed out to long on during an impressive spell by leg-spinner Max Waller before another rain stoppage left Sussex needing 80 from 35 balls.
Laurie Evans smashed five sixes in 40 off 20 balls to give Sussex a chance, but their hopes effectively ended when he was caught at deep point off Lewis Gregory.