According to Mundo Deportivo (h/t Sport Witness), Barca technical secretary Robert Fernandez was at the Santiago Bernabeu on Tuesday to see Kane's Spurs side take on Real Madrid. Sport also reported Fernandez was looking at Christian Eriksen and Davinson Sanchez.
Mundo Deprtivo reported that Fernandez then made the trip to Lisbon to see United tackle Benfica on Wednesday with a view to running the rule over Martial. However, the Frenchman was only on the pitch for the final 14 minutes of his team's 1-0 win.
The Blaugrana want to improve their options in the final third having lost Neymar to Paris Saint-Germain in the summer.
Kane is taking European football by storm with his excellent performances this season, and he impressed at the Bernabeu in the 1-1 draw. As Dan Kilpatrick of ESPN FC noted, there was plenty of talk pre-match about Madrid being keen on the striker too:
Of the two La Liga giants, Real Madrid feels a more natural fit for the England international than Barcelona.
Kane's physical and direct style of forward play aligns well with Los Blancos' classic ethos. It's easy to see him settling into a side that accommodates the power and poise of players like Cristiano Ronaldo and Gareth Bale.
Barcelona have always been a lot more careful and technical in their buildup play than their rivals. And while that's not to say Kane isn't a fine footballer, the Blaugrana typically look for movement and neat interplay from their striker.
Still, Kane's goalscoring record is good enough to make any of Europe's elite clubs look at him. As Squawka Football noted ahead of the match against Real Madrid, the Spurs man has been as prolific as some of the game's best players in 2017:
Martial is the type of forward you would expect to see Barcelona chasing in the future, especially if they want a similar player to Neymar.
Ousmane Dembele, a big-money summer acquisition, can operate anywhere across the front line for the Blaugrana. Martial, while not on Neymar's level, plays the game in a similar way to the Brazilian, as he seeks to get on the ball wide on the left, drive at the full-back and get into the box to score goals.
He's not yet cemented a first-team spot at United under Jose Mourinho, with Marcus Rashford regularly utilised on the left flank early in 2017-18. Journalist Peter Hall feels as though there's a place for both in the setup:
While Barcelona may be taking admiring glances at both players, neither Spurs nor United will be keen on selling such a massive asset.
Kane is Spurs' talisman and well-established as one of the best strikers on the planet, whereas Martial has the potential to go to the top with the right guidance at Old Trafford. If either Premier League side is going to be convinced to make a sale, a massive amount of money would need to be on the table.